diff --git a/.eslintignore b/.eslintignore
index 758aeb91ddbf8..7f38955118ae2 100644
--- a/.eslintignore
+++ b/.eslintignore
@@ -10,3 +10,4 @@ lib/
 # We ignore this file because it uses ES imports which we don't yet use
 # in the Puppeteer src, so it trips up the ESLint-TypeScript parser.
 utils/doclint/generate_types/test/test.ts
+vendor/
diff --git a/.eslintrc.js b/.eslintrc.js
index bc63a76df3c07..84821c4205731 100644
--- a/.eslintrc.js
+++ b/.eslintrc.js
@@ -87,8 +87,14 @@ module.exports = {
         // enforce the variable in a catch block is named error
         "unicorn/catch-error-name": "error",
 
+
         "no-restricted-imports": ["error", {
             patterns: ["*Events"],
+            paths: [{
+                name: "mitt",
+                message:
+                "Import Mitt from the vendored location: vendor/mitt/src/index.js",
+            }],
         }],
         "import/extensions": ["error", "ignorePackages"]
     },
diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 5cf0d56fce334..90f9a1ac0a88a 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -5,6 +5,10 @@
   * [Code reviews](#code-reviews)
   * [Code Style](#code-style)
   * [TypeScript guidelines](#typescript-guidelines)
+  * [Project structure and TypeScript compilation](#project-structure-and-typescript-compilation)
+    - [Shipping CJS and ESM bundles](#shipping-cjs-and-esm-bundles)
+    - [tsconfig for the tests](#tsconfig-for-the-tests)
+    - [Root `tsconfig.json`](#root-tsconfigjson)
   * [API guidelines](#api-guidelines)
   * [Commit Messages](#commit-messages)
   * [Writing Documentation](#writing-documentation)
@@ -85,6 +89,42 @@ npm run tsc
 
 - Try to avoid the use of `any` when possible. Consider `unknown` as a better alternative. You are able to use `any` if needbe, but it will generate an ESLint warning.
 
+## Project structure and TypeScript compilation
+
+The code in Puppeteer is split primarily into two folders:
+
+- `src` contains all source code
+- `vendor` contains all dependencies that we've vendored into the codebase. See the [`vendor/README.md`](https://github.com/puppeteer/puppeteer/blob/main/vendor/README.md) for details.
+
+We structure these using TypeScript's project references, which lets us treat each folder like a standalone TypeScript project.
+
+### Shipping CJS and ESM bundles
+
+Currently Puppeteer ships two bundles; a CommonJS version for Node and an ESM bundle for the browser. Therefore we maintain two `tsconfig` files for each project; `tsconfig.esm.json` and `tsconfig.cjs.json`. At build time we compile twice, once outputting to CJS and another time to output to ESM.
+
+We compile into the `lib` directory which is what we publish on the npm repository and it's structured like so:
+
+```
+lib
+- cjs
+  - puppeteer <== the output of compiling `src/tsconfig.cjs.json`
+  - vendor <== the output of compiling `vendor/tsconfig.cjs.json`
+- esm
+  - puppeteer <== the output of compiling `src/tsconfig.esm.json`
+  - vendor <== the output of compiling `vendor/tsconfig.esm.json`
+```
+
+The main entry point for the Node module Puppeteer is `cjs-entry.js`. This imports `lib/cjs/puppeteer/index.js` and exposes it to Node users.
+
+### tsconfig for the tests
+
+We also maintain `test/tsconfig.test.json`. This is **only used to compile the unit test `*.spec.ts` files**. When the tests are run, we first compile Puppeteer as normal before running the unit tests **against the compiled output**. Doing this lets the test run against the compiled code we ship to users so it gives us more confidence in our compiled output being correct.
+
+### Root `tsconfig.json`
+
+The root `tsconfig.json` exists for the API Extractor; it has to find a `tsconfig.json` in the project's root directory. It is _not_ used for anything else.
+
+
 ## API guidelines
 
 When authoring new API methods, consider the following:
@@ -153,6 +193,9 @@ For all dependencies (both installation and development):
 A barrier for introducing new installation dependencies is especially high:
 - **Do not add** installation dependency unless it's critical to project success.
 
+There are additional considerations for dependencies that are environment agonistic. See the [`vendor/README.md`](https://github.com/puppeteer/puppeteer/blob/main/vendor/README.md) for details.
+
+
 ## Running & Writing Tests
 
 - Every feature should be accompanied by a test.
diff --git a/api-extractor.json b/api-extractor.json
index b388a148a4906..3e7b9e66f625e 100644
--- a/api-extractor.json
+++ b/api-extractor.json
@@ -1,6 +1,6 @@
 {
   "$schema": "https://developer.microsoft.com/json-schemas/api-extractor/v7/api-extractor.schema.json",
-  "mainEntryPointFilePath": "<projectFolder>/lib/cjs/api-docs-entry.d.ts",
+  "mainEntryPointFilePath": "<projectFolder>/lib/cjs/puppeteer/api-docs-entry.d.ts",
   "bundledPackages": [ "devtools-protocol" ],
 
   "apiReport": {
diff --git a/cjs-entry-core.js b/cjs-entry-core.js
index efcdb39027f7e..70e9b88040ff1 100644
--- a/cjs-entry-core.js
+++ b/cjs-entry-core.js
@@ -25,5 +25,5 @@
  * This means that we can publish to CJS and ESM whilst maintaining the expected
  * import behaviour for CJS and ESM users.
  */
-const puppeteerExport = require('./lib/cjs/index-core');
+const puppeteerExport = require('./lib/cjs/puppeteer/index-core');
 module.exports = puppeteerExport.default;
diff --git a/cjs-entry.js b/cjs-entry.js
index 424ffadf1a14e..1bcec7d85aff2 100644
--- a/cjs-entry.js
+++ b/cjs-entry.js
@@ -25,5 +25,5 @@
  * This means that we can publish to CJS and ESM whilst maintaining the expected
  * import behaviour for CJS and ESM users.
  */
-const puppeteerExport = require('./lib/cjs/index');
+const puppeteerExport = require('./lib/cjs/puppeteer/index');
 module.exports = puppeteerExport.default;
diff --git a/install.js b/install.js
index 402a72e0d2f60..5fe1314e4a6e8 100644
--- a/install.js
+++ b/install.js
@@ -29,7 +29,10 @@ const compileTypeScriptIfRequired = require('./typescript-if-required');
 async function download() {
   await compileTypeScriptIfRequired();
   // need to ensure TS is compiled before loading the installer
-  const { downloadBrowser, logPolitely } = require('./lib/cjs/install');
+  const {
+    downloadBrowser,
+    logPolitely,
+  } = require('./lib/cjs/puppeteer/install');
 
   if (process.env.PUPPETEER_SKIP_DOWNLOAD) {
     logPolitely(
diff --git a/package.json b/package.json
index f3a43990e3ede..d71e5fcbae5ca 100644
--- a/package.json
+++ b/package.json
@@ -24,13 +24,12 @@
     "doc": "node utils/doclint/cli.js",
     "clean-lib": "rm -rf lib",
     "tsc": "npm run clean-lib && tsc --version && npm run tsc-cjs && npm run tsc-esm",
-    "tsc-cjs": "tsc -p .",
-    "tsc-esm": "tsc --build tsconfig-esm.json",
-    "typecheck": "tsc -p . --noEmit",
+    "tsc-cjs": "tsc -b src/tsconfig.cjs.json",
+    "tsc-esm": "tsc -b src/tsconfig.esm.json",
     "apply-next-version": "node utils/apply_next_version.js",
     "test-install": "scripts/test-install.sh",
     "generate-docs": "npm run tsc && api-extractor run --local --verbose && api-documenter markdown -i temp -o new-docs",
-    "ensure-new-docs-up-to-date": "npm run generate-docs && exit `git status --porcelain | head -255 | wc -l`",
+    "ensure-new-docs-up-to-date": "npm run generate-docs && git status && exit `git status --porcelain | head -255 | wc -l`",
     "generate-dependency-graph": "echo 'Requires graphviz installed locally!' && depcruise --exclude 'api.ts' --do-not-follow '^node_modules' --output-type dot src/index.ts | dot -T png > dependency-chart.png",
     "ensure-correct-devtools-protocol-revision": "ts-node scripts/ensure-correct-devtools-protocol-package"
   },
@@ -49,7 +48,6 @@
     "extract-zip": "^2.0.0",
     "https-proxy-agent": "^4.0.0",
     "mime": "^2.0.3",
-    "mitt": "^2.0.1",
     "pkg-dir": "^4.2.0",
     "progress": "^2.0.1",
     "proxy-from-env": "^1.0.0",
diff --git a/src/common/EventEmitter.ts b/src/common/EventEmitter.ts
index 73d7787cd533c..3588f1408b6e3 100644
--- a/src/common/EventEmitter.ts
+++ b/src/common/EventEmitter.ts
@@ -1,4 +1,8 @@
-import mitt, { Emitter, EventType, Handler } from 'mitt';
+import mitt, {
+  Emitter,
+  EventType,
+  Handler,
+} from '../../vendor/mitt/src/index.js';
 
 /**
  * @internal
diff --git a/src/tsconfig.cjs.json b/src/tsconfig.cjs.json
new file mode 100644
index 0000000000000..c144b956bf813
--- /dev/null
+++ b/src/tsconfig.cjs.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../tsconfig.base.json",
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "../lib/cjs/puppeteer",
+    "module": "CommonJS"
+  },
+  "references": [
+    { "path": "../vendor/tsconfig.cjs.json"}
+  ]
+}
diff --git a/src/tsconfig.esm.json b/src/tsconfig.esm.json
new file mode 100644
index 0000000000000..487533061f44f
--- /dev/null
+++ b/src/tsconfig.esm.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../tsconfig.base.json",
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "../lib/esm/puppeteer",
+    "module": "esnext"
+  },
+  "references": [
+    { "path": "../vendor/tsconfig.esm.json"}
+  ]
+}
diff --git a/test/EventEmitter.spec.ts b/test/EventEmitter.spec.ts
index ea0189d9e4dff..bf20e7fe8fc28 100644
--- a/test/EventEmitter.spec.ts
+++ b/test/EventEmitter.spec.ts
@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 
-import { EventEmitter } from '../lib/cjs/common/EventEmitter.js';
+import { EventEmitter } from '../lib/cjs/puppeteer/common/EventEmitter.js';
 import sinon from 'sinon';
 import expect from 'expect';
 
diff --git a/test/coverage-utils.js b/test/coverage-utils.js
index 27b06e7492646..add0238a0e8a2 100644
--- a/test/coverage-utils.js
+++ b/test/coverage-utils.js
@@ -39,32 +39,32 @@ const fs = require('fs');
  * part of the TSDoc migration.
  */
 const MODULES_TO_CHECK_FOR_COVERAGE = {
-  Accessibility: '../lib/cjs/common/Accessibility',
-  Browser: '../lib/cjs/common/Browser',
-  BrowserContext: '../lib/cjs/common/Browser',
-  BrowserFetcher: '../lib/cjs/node/BrowserFetcher',
-  CDPSession: '../lib/cjs/common/Connection',
-  ConsoleMessage: '../lib/cjs/common/ConsoleMessage',
-  Coverage: '../lib/cjs/common/Coverage',
-  Dialog: '../lib/cjs/common/Dialog',
-  ElementHandle: '../lib/cjs/common/JSHandle',
-  ExecutionContext: '../lib/cjs/common/ExecutionContext',
-  EventEmitter: '../lib/cjs/common/EventEmitter',
-  FileChooser: '../lib/cjs/common/FileChooser',
-  Frame: '../lib/cjs/common/FrameManager',
-  JSHandle: '../lib/cjs/common/JSHandle',
-  Keyboard: '../lib/cjs/common/Input',
-  Mouse: '../lib/cjs/common/Input',
-  Page: '../lib/cjs/common/Page',
-  Puppeteer: '../lib/cjs/common/Puppeteer',
-  HTTPRequest: '../lib/cjs/common/HTTPRequest',
-  HTTPResponse: '../lib/cjs/common/HTTPResponse',
-  SecurityDetails: '../lib/cjs/common/SecurityDetails',
-  Target: '../lib/cjs/common/Target',
-  TimeoutError: '../lib/cjs/common/Errors',
-  Touchscreen: '../lib/cjs/common/Input',
-  Tracing: '../lib/cjs/common/Tracing',
-  WebWorker: '../lib/cjs/common/WebWorker',
+  Accessibility: '../lib/cjs/puppeteer/common/Accessibility',
+  Browser: '../lib/cjs/puppeteer/common/Browser',
+  BrowserContext: '../lib/cjs/puppeteer/common/Browser',
+  BrowserFetcher: '../lib/cjs/puppeteer/node/BrowserFetcher',
+  CDPSession: '../lib/cjs/puppeteer/common/Connection',
+  ConsoleMessage: '../lib/cjs/puppeteer/common/ConsoleMessage',
+  Coverage: '../lib/cjs/puppeteer/common/Coverage',
+  Dialog: '../lib/cjs/puppeteer/common/Dialog',
+  ElementHandle: '../lib/cjs/puppeteer/common/JSHandle',
+  ExecutionContext: '../lib/cjs/puppeteer/common/ExecutionContext',
+  EventEmitter: '../lib/cjs/puppeteer/common/EventEmitter',
+  FileChooser: '../lib/cjs/puppeteer/common/FileChooser',
+  Frame: '../lib/cjs/puppeteer/common/FrameManager',
+  JSHandle: '../lib/cjs/puppeteer/common/JSHandle',
+  Keyboard: '../lib/cjs/puppeteer/common/Input',
+  Mouse: '../lib/cjs/puppeteer/common/Input',
+  Page: '../lib/cjs/puppeteer/common/Page',
+  Puppeteer: '../lib/cjs/puppeteer/common/Puppeteer',
+  HTTPRequest: '../lib/cjs/puppeteer/common/HTTPRequest',
+  HTTPResponse: '../lib/cjs/puppeteer/common/HTTPResponse',
+  SecurityDetails: '../lib/cjs/puppeteer/common/SecurityDetails',
+  Target: '../lib/cjs/puppeteer/common/Target',
+  TimeoutError: '../lib/cjs/puppeteer/common/Errors',
+  Touchscreen: '../lib/cjs/puppeteer/common/Input',
+  Tracing: '../lib/cjs/puppeteer/common/Tracing',
+  WebWorker: '../lib/cjs/puppeteer/common/WebWorker',
 };
 
 function traceAPICoverage(apiCoverage, className, modulePath) {
diff --git a/test/elementhandle.spec.ts b/test/elementhandle.spec.ts
index e7d221b3b75a8..5bb74a3dbf397 100644
--- a/test/elementhandle.spec.ts
+++ b/test/elementhandle.spec.ts
@@ -24,7 +24,7 @@ import {
 } from './mocha-utils'; // eslint-disable-line import/extensions
 
 import utils from './utils.js';
-import { ElementHandle } from '../lib/cjs/common/JSHandle.js';
+import { ElementHandle } from '../lib/cjs/puppeteer/common/JSHandle.js';
 
 describe('ElementHandle specs', function () {
   setupTestBrowserHooks();
diff --git a/test/keyboard.spec.ts b/test/keyboard.spec.ts
index 9ad47972c7c59..889c97483a04a 100644
--- a/test/keyboard.spec.ts
+++ b/test/keyboard.spec.ts
@@ -23,7 +23,7 @@ import {
   setupTestPageAndContextHooks,
   itFailsFirefox,
 } from './mocha-utils'; // eslint-disable-line import/extensions
-import { KeyInput } from '../lib/cjs/common/USKeyboardLayout.js';
+import { KeyInput } from '../lib/cjs/puppeteer/common/USKeyboardLayout.js';
 
 describe('Keyboard', function () {
   setupTestBrowserHooks();
diff --git a/test/launcher.spec.ts b/test/launcher.spec.ts
index 4e1d623268867..ef3cef9cb9c92 100644
--- a/test/launcher.spec.ts
+++ b/test/launcher.spec.ts
@@ -27,7 +27,7 @@ import {
 import utils from './utils.js';
 import expect from 'expect';
 import rimraf from 'rimraf';
-import { Page } from '../lib/cjs/common/Page.js';
+import { Page } from '../lib/cjs/puppeteer/common/Page.js';
 
 const rmAsync = promisify(rimraf);
 const mkdtempAsync = promisify(fs.mkdtemp);
diff --git a/test/mocha-ts-require.js b/test/mocha-ts-require.js
index 2bf2cc677eba1..a0ac64fa62b7a 100644
--- a/test/mocha-ts-require.js
+++ b/test/mocha-ts-require.js
@@ -1,3 +1,5 @@
+const path = require('path');
+
 require('ts-node').register({
   /**
    * We ignore the lib/ directory because that's already been TypeScript
@@ -5,4 +7,5 @@ require('ts-node').register({
    * the unit tests.
    */
   ignore: ['lib/*', 'node_modules'],
+  project: path.join(__dirname, 'tsconfig.test.json'),
 });
diff --git a/test/mocha-utils.ts b/test/mocha-utils.ts
index 2a26afc98bb45..ae14bbc67e9ee 100644
--- a/test/mocha-utils.ts
+++ b/test/mocha-utils.ts
@@ -19,10 +19,13 @@ import * as path from 'path';
 import * as fs from 'fs';
 import * as os from 'os';
 import sinon from 'sinon';
-import puppeteer from '../lib/cjs/index.js';
-import { Browser, BrowserContext } from '../lib/cjs/common/Browser.js';
-import { Page } from '../lib/cjs/common/Page.js';
-import { Puppeteer } from '../lib/cjs/common/Puppeteer.js';
+import puppeteer from '../lib/cjs/puppeteer/index.js';
+import {
+  Browser,
+  BrowserContext,
+} from '../lib/cjs/puppeteer/common/Browser.js';
+import { Page } from '../lib/cjs/puppeteer/common/Page.js';
+import { Puppeteer } from '../lib/cjs/puppeteer/common/Puppeteer.js';
 import utils from './utils.js';
 import rimraf from 'rimraf';
 
diff --git a/test/mouse.spec.ts b/test/mouse.spec.ts
index 7d47b4cabc120..2670bafdfe670 100644
--- a/test/mouse.spec.ts
+++ b/test/mouse.spec.ts
@@ -21,7 +21,7 @@ import {
   setupTestPageAndContextHooks,
   itFailsFirefox,
 } from './mocha-utils'; // eslint-disable-line import/extensions
-import { KeyInput } from '../lib/cjs/common/USKeyboardLayout.js';
+import { KeyInput } from '../lib/cjs/puppeteer/common/USKeyboardLayout.js';
 
 interface Dimensions {
   x: number;
diff --git a/test/page.spec.ts b/test/page.spec.ts
index 441bc5ac6c178..eb97ceeeacc89 100644
--- a/test/page.spec.ts
+++ b/test/page.spec.ts
@@ -26,8 +26,8 @@ import {
   itFailsFirefox,
   describeFailsFirefox,
 } from './mocha-utils'; // eslint-disable-line import/extensions
-import { Page, Metrics } from '../lib/cjs/common/Page.js';
-import { JSHandle } from '../lib/cjs/common/JSHandle.js';
+import { Page, Metrics } from '../lib/cjs/puppeteer/common/Page.js';
+import { JSHandle } from '../lib/cjs/puppeteer/common/JSHandle.js';
 
 describe('Page', function () {
   setupTestBrowserHooks();
diff --git a/test/target.spec.ts b/test/target.spec.ts
index 7459218dbb5d6..8646a60c8e49e 100644
--- a/test/target.spec.ts
+++ b/test/target.spec.ts
@@ -23,7 +23,7 @@ import {
   setupTestPageAndContextHooks,
   itFailsFirefox,
 } from './mocha-utils'; // eslint-disable-line import/extensions
-import { Target } from '../lib/cjs/common/Target.js';
+import { Target } from '../lib/cjs/puppeteer/common/Target.js';
 
 describe('Target', function () {
   setupTestBrowserHooks();
diff --git a/test/tsconfig.test.json b/test/tsconfig.test.json
new file mode 100644
index 0000000000000..6ae022f65bf01
--- /dev/null
+++ b/test/tsconfig.test.json
@@ -0,0 +1,3 @@
+{
+  "extends": "../tsconfig.base.json",
+}
diff --git a/test/worker.spec.ts b/test/worker.spec.ts
index a4a356bfb3713..2c5827361b52e 100644
--- a/test/worker.spec.ts
+++ b/test/worker.spec.ts
@@ -22,8 +22,8 @@ import {
   describeFailsFirefox,
 } from './mocha-utils'; // eslint-disable-line import/extensions
 import utils from './utils.js';
-import { WebWorker } from '../lib/cjs/common/WebWorker.js';
-import { ConsoleMessage } from '../lib/cjs/common/ConsoleMessage.js';
+import { WebWorker } from '../lib/cjs/puppeteer/common/WebWorker.js';
+import { ConsoleMessage } from '../lib/cjs/puppeteer/common/ConsoleMessage.js';
 const { waitEvent } = utils;
 
 describeFailsFirefox('Workers', function () {
diff --git a/tsconfig.base.json b/tsconfig.base.json
new file mode 100644
index 0000000000000..31a7a463db0bc
--- /dev/null
+++ b/tsconfig.base.json
@@ -0,0 +1,12 @@
+{
+  "compilerOptions": {
+    "esModuleInterop": true,
+    "allowJs": true,
+    "checkJs": true,
+    "target": "ESNext",
+    "moduleResolution": "node",
+    "declaration": true,
+    "declarationMap": true,
+    "resolveJsonModule": true
+  }
+}
diff --git a/tsconfig.json b/tsconfig.json
index 5a62ace19cb13..69717ed6d9b2e 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,17 +1,11 @@
+/**
+ * This configuration only exists for the API Extractor tool. See the details in
+ * CONTRIBUTING.md that describes our TypeScript setup.
+*/
 {
+  "extends": "./tsconfig.base.json",
   "compilerOptions": {
-    "allowJs": true,
-    "checkJs": true,
-    "outDir": "./lib/cjs",
-    "target": "ESNext",
-    "moduleResolution": "node",
-    "module": "CommonJS",
-    "declaration": true,
-    "declarationMap": true,
-    "esModuleInterop": true,
-    "resolveJsonModule": true
+    "noEmit": true
   },
-  "include": [
-    "src"
-  ]
+  "include": ["src"]
 }
diff --git a/utils/doclint/check_public_api/index.js b/utils/doclint/check_public_api/index.js
index 2bd41d4a28280..fa8aa5c9fd06b 100644
--- a/utils/doclint/check_public_api/index.js
+++ b/utils/doclint/check_public_api/index.js
@@ -674,56 +674,56 @@ function compareDocumentations(actual, expected) {
         'Method EventEmitter.emit() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.listenerCount() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.off() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.on() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.once() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.removeListener() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.addListener() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
         'Method EventEmitter.removeAllListeners() event',
         {
           actualName: 'string|symbol',
-          expectedName: 'Object',
+          expectedName: 'EventType',
         },
       ],
       [
diff --git a/utils/doclint/cli.js b/utils/doclint/cli.js
index ef551ac080f84..abc3d2c84d65c 100755
--- a/utils/doclint/cli.js
+++ b/utils/doclint/cli.js
@@ -72,8 +72,12 @@ async function run() {
   const jsSources = [
     ...(await Source.readdir(path.join(PROJECT_DIR, 'lib'))),
     ...(await Source.readdir(path.join(PROJECT_DIR, 'lib', 'cjs'))),
-    ...(await Source.readdir(path.join(PROJECT_DIR, 'lib', 'cjs', 'common'))),
-    ...(await Source.readdir(path.join(PROJECT_DIR, 'lib', 'cjs', 'node'))),
+    ...(await Source.readdir(
+      path.join(PROJECT_DIR, 'lib', 'cjs', 'puppeteer', 'common')
+    )),
+    ...(await Source.readdir(
+      path.join(PROJECT_DIR, 'lib', 'cjs', 'puppeteer', 'node')
+    )),
   ];
   const allSrcCode = [...jsSources, ...tsSourcesNoDefinitions];
   messages.push(...(await checkPublicAPI(page, mdSources, allSrcCode)));
diff --git a/vendor/README.md b/vendor/README.md
new file mode 100644
index 0000000000000..cbb1b43275459
--- /dev/null
+++ b/vendor/README.md
@@ -0,0 +1,13 @@
+# Vendoring third party dependencies
+
+Because we are working towards an agnostic Puppeteer that can run in any environment (see [#6125](https://github.com/puppeteer/puppeteer/issues/6125)) we cannot import common dependencies in a way that relies on Node's resolution to find them. For example, `import mitt from 'mitt'` works fine in Node, but in an ESM build running in the browser, the browser has no idea where to find `'mitt'`.
+
+Therefore we put all common dependencies into this directory, `vendor`. This means there are extra criteria for these dependencies; ideally they will not depend on any other modules. If they do, we should consider an alternative way of managing our dependencies.
+
+The process for updating a vendored dependency is:
+
+1. `npm install {DEP NAME HERE}`
+2. `cp -r node_modules/DEP vendor/DEP`
+3. Update `eslintrc.js` to forbid importing DEP directly (see the `Mitt` rule already defined in there).
+4. Use the new DEP, and run `npm run tsc` to check everything compiles successfully.
+5. If the dep ships as compiled JS, you may need to disable TypeScript checking the file. Add an entry to the `excludes` property of the TSConfig files in `vendor`. (again, see the entry that's already there for Mitt as an example). Don't forget to update both the ESM and CJS config files.
diff --git a/vendor/mitt/README.md b/vendor/mitt/README.md
new file mode 100644
index 0000000000000..b6a80225dfe32
--- /dev/null
+++ b/vendor/mitt/README.md
@@ -0,0 +1,171 @@
+<p align="center">
+  <img src="https://i.imgur.com/BqsX9NT.png" width="300" height="300" alt="mitt">
+  <br>
+  <a href="https://www.npmjs.org/package/mitt"><img src="https://img.shields.io/npm/v/mitt.svg" alt="npm"></a>
+  <img src="https://github.com/developit/mitt/workflows/CI/badge.svg" alt="build status">
+  <a href="https://unpkg.com/mitt/dist/mitt.js"><img src="https://img.badgesize.io/https://unpkg.com/mitt/dist/mitt.js?compression=gzip" alt="gzip size"></a>
+</p>
+
+# Mitt
+
+> Tiny 200b functional event emitter / pubsub.
+
+-   **Microscopic:** weighs less than 200 bytes gzipped
+-   **Useful:** a wildcard `"*"` event type listens to all events
+-   **Familiar:** same names & ideas as [Node's EventEmitter](https://nodejs.org/api/events.html#events_class_eventemitter)
+-   **Functional:** methods don't rely on `this`
+-   **Great Name:** somehow [mitt](https://npm.im/mitt) wasn't taken
+
+Mitt was made for the browser, but works in any JavaScript runtime. It has no dependencies and supports IE9+.
+
+## Table of Contents
+
+-   [Install](#install)
+-   [Usage](#usage)
+-   [Examples & Demos](#examples--demos)
+-   [API](#api)
+-   [Contribute](#contribute)
+-   [License](#license)
+
+## Install
+
+This project uses [node](http://nodejs.org) and [npm](https://npmjs.com). Go check them out if you don't have them locally installed.
+
+```sh
+$ npm install --save mitt
+```
+
+Then with a module bundler like [rollup](http://rollupjs.org/) or [webpack](https://webpack.js.org/), use as you would anything else:
+
+```javascript
+// using ES6 modules
+import mitt from 'mitt'
+
+// using CommonJS modules
+var mitt = require('mitt')
+```
+
+The [UMD](https://github.com/umdjs/umd) build is also available on [unpkg](https://unpkg.com):
+
+```html
+<script src="https://unpkg.com/mitt/dist/mitt.umd.js"></script>
+```
+
+You can find the library on `window.mitt`.
+
+## Usage
+
+```js
+import mitt from 'mitt'
+
+const emitter = mitt()
+
+// listen to an event
+emitter.on('foo', e => console.log('foo', e) )
+
+// listen to all events
+emitter.on('*', (type, e) => console.log(type, e) )
+
+// fire an event
+emitter.emit('foo', { a: 'b' })
+
+// working with handler references:
+function onFoo() {}
+emitter.on('foo', onFoo)   // listen
+emitter.off('foo', onFoo)  // unlisten
+```
+
+### Typescript
+
+```ts
+import mitt from 'mitt';
+const emitter: mitt.Emitter = mitt();
+```
+
+## Examples & Demos
+
+<a href="http://codepen.io/developit/pen/rjMEwW?editors=0110">
+  <b>Preact + Mitt Codepen Demo</b>
+  <br>
+  <img src="https://i.imgur.com/CjBgOfJ.png" width="278" alt="preact + mitt preview">
+</a>
+
+* * *
+
+## API
+
+<!-- Generated by documentation.js. Update this documentation by updating the source code. -->
+
+#### Table of Contents
+
+-   [mitt](#mitt)
+-   [on](#on)
+    -   [Parameters](#parameters)
+-   [off](#off)
+    -   [Parameters](#parameters-1)
+-   [emit](#emit)
+    -   [Parameters](#parameters-2)
+
+### mitt
+
+Mitt: Tiny (~200b) functional event emitter / pubsub.
+
+Returns **Mitt** 
+
+### on
+
+Register an event handler for the given type.
+
+#### Parameters
+
+-   `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol))** Type of event to listen for, or `"*"` for all events
+-   `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function)** Function to call in response to given event
+
+### off
+
+Remove an event handler for the given type.
+
+#### Parameters
+
+-   `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol))** Type of event to unregister `handler` from, or `"*"`
+-   `handler` **[Function](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Statements/function)** Handler function to remove
+
+### emit
+
+Invoke all handlers for the given type.
+If present, `"*"` handlers are invoked after type-matched handlers.
+
+Note: Manually firing "\*" handlers is not supported.
+
+#### Parameters
+
+-   `type` **([string](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/String) \| [symbol](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Symbol))** The event type to invoke
+-   `evt` **Any?** Any value (object is recommended and powerful), passed to each handler
+
+## Contribute
+
+First off, thanks for taking the time to contribute!
+Now, take a moment to be sure your contributions make sense to everyone else.
+
+### Reporting Issues
+
+Found a problem? Want a new feature? First of all see if your issue or idea has [already been reported](../../issues).
+If don't, just open a [new clear and descriptive issue](../../issues/new).
+
+### Submitting pull requests
+
+Pull requests are the greatest contributions, so be sure they are focused in scope, and do avoid unrelated commits.
+
+-   Fork it!
+-   Clone your fork: `git clone https://github.com/<your-username>/mitt`
+-   Navigate to the newly cloned directory: `cd mitt`
+-   Create a new branch for the new feature: `git checkout -b my-new-feature`
+-   Install the tools necessary for development: `npm install`
+-   Make your changes.
+-   Commit your changes: `git commit -am 'Add some feature'`
+-   Push to the branch: `git push origin my-new-feature`
+-   Submit a pull request with full remarks documenting your changes.
+
+## License
+
+[MIT License](https://opensource.org/licenses/MIT) © [Jason Miller](https://jasonformat.com/)
diff --git a/vendor/mitt/dist/index.d.ts b/vendor/mitt/dist/index.d.ts
new file mode 100644
index 0000000000000..b37905bcf57f9
--- /dev/null
+++ b/vendor/mitt/dist/index.d.ts
@@ -0,0 +1,19 @@
+export declare type EventType = string | symbol;
+export declare type Handler = (event?: any) => void;
+export declare type WildcardHandler = (type: EventType, event?: any) => void;
+export declare type EventHandlerList = Array<Handler>;
+export declare type WildCardEventHandlerList = Array<WildcardHandler>;
+export declare type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;
+export interface Emitter {
+    on(type: EventType, handler: Handler): void;
+    on(type: '*', handler: WildcardHandler): void;
+    off(type: EventType, handler: Handler): void;
+    off(type: '*', handler: WildcardHandler): void;
+    emit<T = any>(type: EventType, event?: T): void;
+    emit(type: '*', event?: any): void;
+}
+/** Mitt: Tiny (~200b) functional event emitter / pubsub.
+ *  @name mitt
+ *  @returns {Mitt}
+ */
+export default function mitt(all?: EventHandlerMap): Emitter;
diff --git a/vendor/mitt/dist/mitt.es.js b/vendor/mitt/dist/mitt.es.js
new file mode 100644
index 0000000000000..74aaf3a2413c1
--- /dev/null
+++ b/vendor/mitt/dist/mitt.es.js
@@ -0,0 +1,2 @@
+export default function(n){return n=n||new Map,{on:function(t,e){var i=n.get(t);i&&i.push(e)||n.set(t,[e])},off:function(t,e){var i=n.get(t);i&&i.splice(i.indexOf(e)>>>0,1)},emit:function(t,e){(n.get(t)||[]).slice().map(function(n){n(e)}),(n.get("*")||[]).slice().map(function(n){n(t,e)})}}}
+//# sourceMappingURL=mitt.es.js.map
diff --git a/vendor/mitt/dist/mitt.es.js.map b/vendor/mitt/dist/mitt.es.js.map
new file mode 100644
index 0000000000000..0f1670de46272
--- /dev/null
+++ b/vendor/mitt/dist/mitt.es.js.map
@@ -0,0 +1 @@
+{"version":3,"file":"mitt.es.js","sources":["../src/index.ts"],"sourcesContent":["export type EventType = string | symbol;\n\n// An event handler can take an optional event argument\n// and should not return a value\nexport type Handler = (event?: any) => void;\nexport type WildcardHandler= (type: EventType, event?: any) => void\n\n// An array of all currently registered event handlers for a type\nexport type EventHandlerList = Array<Handler>;\nexport type WildCardEventHandlerList = Array<WildcardHandler>;\n\n// A map of event types and their corresponding event handlers.\nexport type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;\n\nexport interface Emitter {\n\ton(type: EventType, handler: Handler): void;\n\ton(type: '*', handler: WildcardHandler): void;\n\n\toff(type: EventType, handler: Handler): void;\n\toff(type: '*', handler: WildcardHandler): void;\n\n\temit<T = any>(type: EventType, event?: T): void;\n\temit(type: '*', event?: any): void;\n}\n\n/** Mitt: Tiny (~200b) functional event emitter / pubsub.\n *  @name mitt\n *  @returns {Mitt}\n */\nexport default function mitt(all?: EventHandlerMap): Emitter {\n\tall = all || new Map();\n\n\treturn {\n\n\t\t/**\n\t\t * Register an event handler for the given type.\n\t\t * @param {string|symbol} type Type of event to listen for, or `\"*\"` for all events\n\t\t * @param {Function} handler Function to call in response to given event\n\t\t * @memberOf mitt\n\t\t */\n\t\ton(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tconst added = handlers && handlers.push(handler);\n\t\t\tif (!added) {\n\t\t\t\tall.set(type, [handler]);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Remove an event handler for the given type.\n\t\t *\n\t\t * @param {string|symbol} type Type of event to unregister `handler` from, or `\"*\"`\n\t\t * @param {Function} handler Handler function to remove\n\t\t * @memberOf mitt\n\t\t */\n\t\toff(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tif (handlers) {\n\t\t\t\thandlers.splice(handlers.indexOf(handler) >>> 0, 1);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Invoke all handlers for the given type.\n\t\t * If present, `\"*\"` handlers are invoked after type-matched handlers.\n\t\t *\n\t\t * Note: Manually firing \"*\" handlers is not supported.\n\t\t *\n\t\t * @param {string|symbol} type The event type to invoke\n\t\t * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler\n\t\t * @memberOf mitt\n\t\t */\n\t\temit(type: EventType, evt: any) {\n\t\t\t((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });\n\t\t\t((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });\n\t\t}\n\t};\n}\n"],"names":["all","Map","on","type","handler","handlers","get","push","set","off","splice","indexOf","emit","evt","slice","map"],"mappings":"wBA6B6BA,GAG5B,OAFAA,EAAMA,GAAO,IAAIC,IAEV,CAQNC,YAAGC,EAAiBC,GACnB,IAAMC,EAAWL,EAAIM,IAAIH,GACXE,GAAYA,EAASE,KAAKH,IAEvCJ,EAAIQ,IAAIL,EAAM,CAACC,KAWjBK,aAAIN,EAAiBC,GACpB,IAAMC,EAAWL,EAAIM,IAAIH,GACrBE,GACHA,EAASK,OAAOL,EAASM,QAAQP,KAAa,EAAG,IAcnDQ,cAAKT,EAAiBU,IACnBb,EAAIM,IAAIH,IAAS,IAAyBW,QAAQC,IAAI,SAACX,GAAcA,EAAQS,MAC7Eb,EAAIM,IAAI,MAAQ,IAAiCQ,QAAQC,IAAI,SAACX,GAAcA,EAAQD,EAAMU"}
\ No newline at end of file
diff --git a/vendor/mitt/dist/mitt.js b/vendor/mitt/dist/mitt.js
new file mode 100644
index 0000000000000..fdfe692346d73
--- /dev/null
+++ b/vendor/mitt/dist/mitt.js
@@ -0,0 +1,2 @@
+module.exports=function(n){return n=n||new Map,{on:function(e,t){var i=n.get(e);i&&i.push(t)||n.set(e,[t])},off:function(e,t){var i=n.get(e);i&&i.splice(i.indexOf(t)>>>0,1)},emit:function(e,t){(n.get(e)||[]).slice().map(function(n){n(t)}),(n.get("*")||[]).slice().map(function(n){n(e,t)})}}};
+//# sourceMappingURL=mitt.js.map
diff --git a/vendor/mitt/dist/mitt.js.map b/vendor/mitt/dist/mitt.js.map
new file mode 100644
index 0000000000000..e5d45cedaccc2
--- /dev/null
+++ b/vendor/mitt/dist/mitt.js.map
@@ -0,0 +1 @@
+{"version":3,"file":"mitt.js","sources":["../src/index.ts"],"sourcesContent":["export type EventType = string | symbol;\n\n// An event handler can take an optional event argument\n// and should not return a value\nexport type Handler = (event?: any) => void;\nexport type WildcardHandler= (type: EventType, event?: any) => void\n\n// An array of all currently registered event handlers for a type\nexport type EventHandlerList = Array<Handler>;\nexport type WildCardEventHandlerList = Array<WildcardHandler>;\n\n// A map of event types and their corresponding event handlers.\nexport type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;\n\nexport interface Emitter {\n\ton(type: EventType, handler: Handler): void;\n\ton(type: '*', handler: WildcardHandler): void;\n\n\toff(type: EventType, handler: Handler): void;\n\toff(type: '*', handler: WildcardHandler): void;\n\n\temit<T = any>(type: EventType, event?: T): void;\n\temit(type: '*', event?: any): void;\n}\n\n/** Mitt: Tiny (~200b) functional event emitter / pubsub.\n *  @name mitt\n *  @returns {Mitt}\n */\nexport default function mitt(all?: EventHandlerMap): Emitter {\n\tall = all || new Map();\n\n\treturn {\n\n\t\t/**\n\t\t * Register an event handler for the given type.\n\t\t * @param {string|symbol} type Type of event to listen for, or `\"*\"` for all events\n\t\t * @param {Function} handler Function to call in response to given event\n\t\t * @memberOf mitt\n\t\t */\n\t\ton(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tconst added = handlers && handlers.push(handler);\n\t\t\tif (!added) {\n\t\t\t\tall.set(type, [handler]);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Remove an event handler for the given type.\n\t\t *\n\t\t * @param {string|symbol} type Type of event to unregister `handler` from, or `\"*\"`\n\t\t * @param {Function} handler Handler function to remove\n\t\t * @memberOf mitt\n\t\t */\n\t\toff(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tif (handlers) {\n\t\t\t\thandlers.splice(handlers.indexOf(handler) >>> 0, 1);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Invoke all handlers for the given type.\n\t\t * If present, `\"*\"` handlers are invoked after type-matched handlers.\n\t\t *\n\t\t * Note: Manually firing \"*\" handlers is not supported.\n\t\t *\n\t\t * @param {string|symbol} type The event type to invoke\n\t\t * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler\n\t\t * @memberOf mitt\n\t\t */\n\t\temit(type: EventType, evt: any) {\n\t\t\t((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });\n\t\t\t((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });\n\t\t}\n\t};\n}\n"],"names":["all","Map","on","type","handler","handlers","get","push","set","off","splice","indexOf","emit","evt","slice","map"],"mappings":"wBA6B6BA,GAG5B,OAFAA,EAAMA,GAAO,IAAIC,IAEV,CAQNC,YAAGC,EAAiBC,GACnB,IAAMC,EAAWL,EAAIM,IAAIH,GACXE,GAAYA,EAASE,KAAKH,IAEvCJ,EAAIQ,IAAIL,EAAM,CAACC,KAWjBK,aAAIN,EAAiBC,GACpB,IAAMC,EAAWL,EAAIM,IAAIH,GACrBE,GACHA,EAASK,OAAOL,EAASM,QAAQP,KAAa,EAAG,IAcnDQ,cAAKT,EAAiBU,IACnBb,EAAIM,IAAIH,IAAS,IAAyBW,QAAQC,IAAI,SAACX,GAAcA,EAAQS,MAC7Eb,EAAIM,IAAI,MAAQ,IAAiCQ,QAAQC,IAAI,SAACX,GAAcA,EAAQD,EAAMU"}
\ No newline at end of file
diff --git a/vendor/mitt/dist/mitt.modern.js b/vendor/mitt/dist/mitt.modern.js
new file mode 100644
index 0000000000000..ccafa5a569689
--- /dev/null
+++ b/vendor/mitt/dist/mitt.modern.js
@@ -0,0 +1,2 @@
+export default function(e){return e=e||new Map,{on(t,n){const s=e.get(t);s&&s.push(n)||e.set(t,[n])},off(t,n){const s=e.get(t);s&&s.splice(s.indexOf(n)>>>0,1)},emit(t,n){(e.get(t)||[]).slice().map(e=>{e(n)}),(e.get("*")||[]).slice().map(e=>{e(t,n)})}}}
+//# sourceMappingURL=mitt.modern.js.map
diff --git a/vendor/mitt/dist/mitt.modern.js.map b/vendor/mitt/dist/mitt.modern.js.map
new file mode 100644
index 0000000000000..650d79e5b50a9
--- /dev/null
+++ b/vendor/mitt/dist/mitt.modern.js.map
@@ -0,0 +1 @@
+{"version":3,"file":"mitt.modern.js","sources":["../src/index.ts"],"sourcesContent":["export type EventType = string | symbol;\n\n// An event handler can take an optional event argument\n// and should not return a value\nexport type Handler = (event?: any) => void;\nexport type WildcardHandler= (type: EventType, event?: any) => void\n\n// An array of all currently registered event handlers for a type\nexport type EventHandlerList = Array<Handler>;\nexport type WildCardEventHandlerList = Array<WildcardHandler>;\n\n// A map of event types and their corresponding event handlers.\nexport type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;\n\nexport interface Emitter {\n\ton(type: EventType, handler: Handler): void;\n\ton(type: '*', handler: WildcardHandler): void;\n\n\toff(type: EventType, handler: Handler): void;\n\toff(type: '*', handler: WildcardHandler): void;\n\n\temit<T = any>(type: EventType, event?: T): void;\n\temit(type: '*', event?: any): void;\n}\n\n/** Mitt: Tiny (~200b) functional event emitter / pubsub.\n *  @name mitt\n *  @returns {Mitt}\n */\nexport default function mitt(all?: EventHandlerMap): Emitter {\n\tall = all || new Map();\n\n\treturn {\n\n\t\t/**\n\t\t * Register an event handler for the given type.\n\t\t * @param {string|symbol} type Type of event to listen for, or `\"*\"` for all events\n\t\t * @param {Function} handler Function to call in response to given event\n\t\t * @memberOf mitt\n\t\t */\n\t\ton(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tconst added = handlers && handlers.push(handler);\n\t\t\tif (!added) {\n\t\t\t\tall.set(type, [handler]);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Remove an event handler for the given type.\n\t\t *\n\t\t * @param {string|symbol} type Type of event to unregister `handler` from, or `\"*\"`\n\t\t * @param {Function} handler Handler function to remove\n\t\t * @memberOf mitt\n\t\t */\n\t\toff(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tif (handlers) {\n\t\t\t\thandlers.splice(handlers.indexOf(handler) >>> 0, 1);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Invoke all handlers for the given type.\n\t\t * If present, `\"*\"` handlers are invoked after type-matched handlers.\n\t\t *\n\t\t * Note: Manually firing \"*\" handlers is not supported.\n\t\t *\n\t\t * @param {string|symbol} type The event type to invoke\n\t\t * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler\n\t\t * @memberOf mitt\n\t\t */\n\t\temit(type: EventType, evt: any) {\n\t\t\t((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });\n\t\t\t((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });\n\t\t}\n\t};\n}\n"],"names":["all","Map","on","type","handler","handlers","get","push","set","off","splice","indexOf","emit","evt","slice","map"],"mappings":"wBA6B6BA,GAG5B,OAFAA,EAAMA,GAAO,IAAIC,IAEV,CAQNC,GAAGC,EAAiBC,GACnB,MAAMC,EAAWL,EAAIM,IAAIH,GACXE,GAAYA,EAASE,KAAKH,IAEvCJ,EAAIQ,IAAIL,EAAM,CAACC,KAWjBK,IAAIN,EAAiBC,GACpB,MAAMC,EAAWL,EAAIM,IAAIH,GACrBE,GACHA,EAASK,OAAOL,EAASM,QAAQP,KAAa,EAAG,IAcnDQ,KAAKT,EAAiBU,IACnBb,EAAIM,IAAIH,IAAS,IAAyBW,QAAQC,IAAKX,IAAcA,EAAQS,MAC7Eb,EAAIM,IAAI,MAAQ,IAAiCQ,QAAQC,IAAKX,IAAcA,EAAQD,EAAMU"}
\ No newline at end of file
diff --git a/vendor/mitt/dist/mitt.umd.js b/vendor/mitt/dist/mitt.umd.js
new file mode 100644
index 0000000000000..cf39868329fd7
--- /dev/null
+++ b/vendor/mitt/dist/mitt.umd.js
@@ -0,0 +1,2 @@
+!function(e,n){"object"==typeof exports&&"undefined"!=typeof module?module.exports=n():"function"==typeof define&&define.amd?define(n):(e=e||self).mitt=n()}(this,function(){return function(e){return e=e||new Map,{on:function(n,t){var f=e.get(n);f&&f.push(t)||e.set(n,[t])},off:function(n,t){var f=e.get(n);f&&f.splice(f.indexOf(t)>>>0,1)},emit:function(n,t){(e.get(n)||[]).slice().map(function(e){e(t)}),(e.get("*")||[]).slice().map(function(e){e(n,t)})}}}});
+//# sourceMappingURL=mitt.umd.js.map
diff --git a/vendor/mitt/dist/mitt.umd.js.map b/vendor/mitt/dist/mitt.umd.js.map
new file mode 100644
index 0000000000000..b5aaf64a43593
--- /dev/null
+++ b/vendor/mitt/dist/mitt.umd.js.map
@@ -0,0 +1 @@
+{"version":3,"file":"mitt.umd.js","sources":["../src/index.ts"],"sourcesContent":["export type EventType = string | symbol;\n\n// An event handler can take an optional event argument\n// and should not return a value\nexport type Handler = (event?: any) => void;\nexport type WildcardHandler= (type: EventType, event?: any) => void\n\n// An array of all currently registered event handlers for a type\nexport type EventHandlerList = Array<Handler>;\nexport type WildCardEventHandlerList = Array<WildcardHandler>;\n\n// A map of event types and their corresponding event handlers.\nexport type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;\n\nexport interface Emitter {\n\ton(type: EventType, handler: Handler): void;\n\ton(type: '*', handler: WildcardHandler): void;\n\n\toff(type: EventType, handler: Handler): void;\n\toff(type: '*', handler: WildcardHandler): void;\n\n\temit<T = any>(type: EventType, event?: T): void;\n\temit(type: '*', event?: any): void;\n}\n\n/** Mitt: Tiny (~200b) functional event emitter / pubsub.\n *  @name mitt\n *  @returns {Mitt}\n */\nexport default function mitt(all?: EventHandlerMap): Emitter {\n\tall = all || new Map();\n\n\treturn {\n\n\t\t/**\n\t\t * Register an event handler for the given type.\n\t\t * @param {string|symbol} type Type of event to listen for, or `\"*\"` for all events\n\t\t * @param {Function} handler Function to call in response to given event\n\t\t * @memberOf mitt\n\t\t */\n\t\ton(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tconst added = handlers && handlers.push(handler);\n\t\t\tif (!added) {\n\t\t\t\tall.set(type, [handler]);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Remove an event handler for the given type.\n\t\t *\n\t\t * @param {string|symbol} type Type of event to unregister `handler` from, or `\"*\"`\n\t\t * @param {Function} handler Handler function to remove\n\t\t * @memberOf mitt\n\t\t */\n\t\toff(type: EventType, handler: Handler) {\n\t\t\tconst handlers = all.get(type);\n\t\t\tif (handlers) {\n\t\t\t\thandlers.splice(handlers.indexOf(handler) >>> 0, 1);\n\t\t\t}\n\t\t},\n\n\t\t/**\n\t\t * Invoke all handlers for the given type.\n\t\t * If present, `\"*\"` handlers are invoked after type-matched handlers.\n\t\t *\n\t\t * Note: Manually firing \"*\" handlers is not supported.\n\t\t *\n\t\t * @param {string|symbol} type The event type to invoke\n\t\t * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler\n\t\t * @memberOf mitt\n\t\t */\n\t\temit(type: EventType, evt: any) {\n\t\t\t((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });\n\t\t\t((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });\n\t\t}\n\t};\n}\n"],"names":["all","Map","on","type","handler","handlers","get","push","set","off","splice","indexOf","emit","evt","slice","map"],"mappings":"6LA6B6BA,GAG5B,OAFAA,EAAMA,GAAO,IAAIC,IAEV,CAQNC,YAAGC,EAAiBC,GACnB,IAAMC,EAAWL,EAAIM,IAAIH,GACXE,GAAYA,EAASE,KAAKH,IAEvCJ,EAAIQ,IAAIL,EAAM,CAACC,KAWjBK,aAAIN,EAAiBC,GACpB,IAAMC,EAAWL,EAAIM,IAAIH,GACrBE,GACHA,EAASK,OAAOL,EAASM,QAAQP,KAAa,EAAG,IAcnDQ,cAAKT,EAAiBU,IACnBb,EAAIM,IAAIH,IAAS,IAAyBW,QAAQC,IAAI,SAACX,GAAcA,EAAQS,MAC7Eb,EAAIM,IAAI,MAAQ,IAAiCQ,QAAQC,IAAI,SAACX,GAAcA,EAAQD,EAAMU"}
\ No newline at end of file
diff --git a/vendor/mitt/package.json b/vendor/mitt/package.json
new file mode 100644
index 0000000000000..0e1e01b86f541
--- /dev/null
+++ b/vendor/mitt/package.json
@@ -0,0 +1,125 @@
+{
+  "_from": "mitt@^2.0.1",
+  "_id": "mitt@2.0.1",
+  "_inBundle": false,
+  "_integrity": "sha512-FhuJY+tYHLnPcBHQhbUFzscD5512HumCPE4URXZUgPi3IvOJi4Xva5IIgy3xX56GqCmw++MAm5UURG6kDBYTdg==",
+  "_location": "/mitt",
+  "_phantomChildren": {},
+  "_requested": {
+    "type": "range",
+    "registry": true,
+    "raw": "mitt@^2.0.1",
+    "name": "mitt",
+    "escapedName": "mitt",
+    "rawSpec": "^2.0.1",
+    "saveSpec": null,
+    "fetchSpec": "^2.0.1"
+  },
+  "_requiredBy": [
+    "/"
+  ],
+  "_resolved": "https://registry.npmjs.org/mitt/-/mitt-2.0.1.tgz",
+  "_shasum": "9e8a075b4daae82dd91aac155a0ece40ca7cb393",
+  "_spec": "mitt@^2.0.1",
+  "_where": "/Users/jacktfranklin/src/puppeteer",
+  "authors": [
+    "Jason Miller <jason@developit.ca>"
+  ],
+  "bugs": {
+    "url": "https://github.com/developit/mitt/issues"
+  },
+  "bundleDependencies": false,
+  "deprecated": false,
+  "description": "Tiny 200b functional Event Emitter / pubsub.",
+  "devDependencies": {
+    "@types/chai": "^4.2.11",
+    "@types/mocha": "^7.0.2",
+    "@types/sinon": "^9.0.4",
+    "@types/sinon-chai": "^3.2.4",
+    "@typescript-eslint/eslint-plugin": "^3.0.1",
+    "@typescript-eslint/parser": "^3.0.1",
+    "chai": "^4.2.0",
+    "documentation": "^13.0.0",
+    "eslint": "^7.1.0",
+    "eslint-config-developit": "^1.2.0",
+    "esm": "^3.2.25",
+    "microbundle": "^0.12.0",
+    "mocha": "^7.2.0",
+    "npm-run-all": "^4.1.5",
+    "rimraf": "^3.0.2",
+    "sinon": "^9.0.2",
+    "sinon-chai": "^3.5.0",
+    "ts-node": "^8.10.1",
+    "typescript": "^3.9.3"
+  },
+  "eslintConfig": {
+    "extends": [
+      "developit",
+      "plugin:@typescript-eslint/eslint-recommended",
+      "plugin:@typescript-eslint/recommended"
+    ],
+    "parser": "@typescript-eslint/parser",
+    "parserOptions": {
+      "sourceType": "module"
+    },
+    "env": {
+      "browser": true,
+      "mocha": true,
+      "jest": false,
+      "es6": true
+    },
+    "globals": {
+      "expect": true
+    },
+    "rules": {
+      "semi": [
+        2,
+        "always"
+      ],
+      "jest/valid-expect": 0,
+      "@typescript-eslint/no-explicit-any": 0,
+      "@typescript-eslint/explicit-function-return-type": 0,
+      "@typescript-eslint/explicit-module-boundary-types": 0,
+      "@typescript-eslint/no-empty-function": 0
+    }
+  },
+  "eslintIgnore": [
+    "dist"
+  ],
+  "esmodules": "dist/mitt.modern.js",
+  "files": [
+    "src",
+    "dist"
+  ],
+  "homepage": "https://github.com/developit/mitt",
+  "jsnext:main": "dist/mitt.es.js",
+  "keywords": [
+    "events",
+    "eventemitter",
+    "emitter",
+    "pubsub"
+  ],
+  "license": "MIT",
+  "main": "dist/mitt.js",
+  "module": "dist/mitt.es.js",
+  "name": "mitt",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/developit/mitt.git"
+  },
+  "scripts": {
+    "build": "npm-run-all --silent clean -p bundle -s docs",
+    "bundle": "microbundle",
+    "clean": "rimraf dist",
+    "docs": "documentation readme src/index.ts --section API -q --parse-extension ts",
+    "lint": "eslint src test --ext ts --ext js",
+    "release": "npm run -s build -s && npm t && git commit -m $npm_package_version && git tag $npm_package_version && git push && git push --tags && npm publish",
+    "test": "npm-run-all --silent typecheck lint testonly",
+    "testonly": "mocha --require esm test/**/*.js",
+    "typecheck": "tsc **/*.ts --noEmit"
+  },
+  "source": "src/index.ts",
+  "typings": "dist/index.d.ts",
+  "umd:main": "dist/mitt.umd.js",
+  "version": "2.0.1"
+}
diff --git a/vendor/mitt/src/index.ts b/vendor/mitt/src/index.ts
new file mode 100644
index 0000000000000..cfb1cf386cdbd
--- /dev/null
+++ b/vendor/mitt/src/index.ts
@@ -0,0 +1,78 @@
+export type EventType = string | symbol;
+
+// An event handler can take an optional event argument
+// and should not return a value
+export type Handler = (event?: any) => void;
+export type WildcardHandler= (type: EventType, event?: any) => void
+
+// An array of all currently registered event handlers for a type
+export type EventHandlerList = Array<Handler>;
+export type WildCardEventHandlerList = Array<WildcardHandler>;
+
+// A map of event types and their corresponding event handlers.
+export type EventHandlerMap = Map<EventType, EventHandlerList | WildCardEventHandlerList>;
+
+export interface Emitter {
+	on(type: EventType, handler: Handler): void;
+	on(type: '*', handler: WildcardHandler): void;
+
+	off(type: EventType, handler: Handler): void;
+	off(type: '*', handler: WildcardHandler): void;
+
+	emit<T = any>(type: EventType, event?: T): void;
+	emit(type: '*', event?: any): void;
+}
+
+/** Mitt: Tiny (~200b) functional event emitter / pubsub.
+ *  @name mitt
+ *  @returns {Mitt}
+ */
+export default function mitt(all?: EventHandlerMap): Emitter {
+	all = all || new Map();
+
+	return {
+
+		/**
+		 * Register an event handler for the given type.
+		 * @param {string|symbol} type Type of event to listen for, or `"*"` for all events
+		 * @param {Function} handler Function to call in response to given event
+		 * @memberOf mitt
+		 */
+		on(type: EventType, handler: Handler) {
+			const handlers = all.get(type);
+			const added = handlers && handlers.push(handler);
+			if (!added) {
+				all.set(type, [handler]);
+			}
+		},
+
+		/**
+		 * Remove an event handler for the given type.
+		 *
+		 * @param {string|symbol} type Type of event to unregister `handler` from, or `"*"`
+		 * @param {Function} handler Handler function to remove
+		 * @memberOf mitt
+		 */
+		off(type: EventType, handler: Handler) {
+			const handlers = all.get(type);
+			if (handlers) {
+				handlers.splice(handlers.indexOf(handler) >>> 0, 1);
+			}
+		},
+
+		/**
+		 * Invoke all handlers for the given type.
+		 * If present, `"*"` handlers are invoked after type-matched handlers.
+		 *
+		 * Note: Manually firing "*" handlers is not supported.
+		 *
+		 * @param {string|symbol} type The event type to invoke
+		 * @param {Any} [evt] Any value (object is recommended and powerful), passed to each handler
+		 * @memberOf mitt
+		 */
+		emit(type: EventType, evt: any) {
+			((all.get(type) || []) as EventHandlerList).slice().map((handler) => { handler(evt); });
+			((all.get('*') || []) as WildCardEventHandlerList).slice().map((handler) => { handler(type, evt); });
+		}
+	};
+}
diff --git a/vendor/tsconfig.cjs.json b/vendor/tsconfig.cjs.json
new file mode 100644
index 0000000000000..f73a8d57d0115
--- /dev/null
+++ b/vendor/tsconfig.cjs.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../tsconfig.base.json",
+  "exclude": [
+    "mitt/dist"
+  ],
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "../lib/cjs/vendor",
+    "module": "CommonJS"
+  }
+}
diff --git a/vendor/tsconfig.esm.json b/vendor/tsconfig.esm.json
new file mode 100644
index 0000000000000..1f0bae8e3d2db
--- /dev/null
+++ b/vendor/tsconfig.esm.json
@@ -0,0 +1,11 @@
+{
+  "extends": "../tsconfig.base.json",
+  "exclude": [
+    "mitt/dist"
+  ],
+  "compilerOptions": {
+    "composite": true,
+    "outDir": "../lib/esm/vendor",
+    "module": "esnext"
+  }
+}