add note about preset-env to a few missed plugins (#2485)

Fixes #2483

docs/plugin-proposal-class-properties.md

@@ -4,6 +4,8 @@ title: @babel/plugin-proposal-class-properties
 sidebar_label: class-properties
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env`
+
 ## Example
 
 Below is a class with four class properties which will be transformed.

docs/plugin-proposal-private-methods.md

@@ -4,6 +4,8 @@ title: @babel/plugin-proposal-private-methods
 sidebar_label: private-methods
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env`
+
 <details>
 <summary>History</summary>
 | Version | Changes |

docs/plugin-transform-modules-amd.md

@@ -4,6 +4,8 @@ title: @babel/plugin-transform-modules-amd
 sidebar_label: AMD
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env` under the `modules` option
+
 This plugin transforms ECMAScript modules to [AMD](https://github.com/amdjs/amdjs-api/blob/master/AMD.md). Note that only the _syntax_ of import/export statements (`import "./mod.js"`) and import expressions (`import('./mod.js')`) is transformed, as Babel is unaware of the different resolution algorithms between implementations of ECMAScript modules and AMD.
 
 ## Example

docs/plugin-transform-modules-commonjs.md

@@ -4,6 +4,8 @@ title: @babel/plugin-transform-modules-commonjs
 sidebar_label: Common JS
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env` under the `modules` option
+
 This plugin transforms ECMAScript modules to [CommonJS](http://wiki.commonjs.org/wiki/Modules/1.1). Note that only the _syntax_ of import/export statements (`import "./mod.js"`) and import expressions (`import('./mod.js')`) is transformed, as Babel is unaware of different resolution algorithms between implementations of ECMAScript modules and CommonJS.
 
 ## Example

docs/plugin-transform-modules-systemjs.md

@@ -4,6 +4,8 @@ title: @babel/plugin-transform-modules-systemjs
 sidebar_label: SystemJS
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env` under the `modules` option
+
 This plugin transforms ECMAScript modules to [SystemJS](https://github.com/systemjs/systemjs/blob/master/docs/system-register.md). Note that only the _syntax_ of import/export statements (`import "./mod.js"`) and import expressions (`import('./mod.js')`) is transformed, as Babel is unaware of different resolution algorithms between implementations of ECMAScript modules and SystemJS.
 
 ## Example

docs/plugin-transform-modules-umd.md

@@ -4,6 +4,8 @@ title: @babel/plugin-transform-modules-umd
 sidebar_label: UMD
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env` under the `modules` option
+
 This plugin transforms ES2015 modules to [UMD](https://github.com/umdjs/umd). Note that only the _syntax_ of import/export statements (`import "./mod.js"`) is transformed, as Babel is unaware of different resolution algorithms between implementations of ES2015 modules and UMD.
 
 ⚠️ This plugin does not support dynamic import (`import('./lazy.js')`).

docs/plugin-transform-regenerator.md

@@ -4,6 +4,8 @@ title: @babel/plugin-transform-regenerator
 sidebar_label: regenerator
 ---
 
+> **NOTE**: This plugin is included in `@babel/preset-env`
+
 ## Example
 
 **In**

docs/preset-env.md

@@ -30,7 +30,7 @@ yarn add @babel/preset-env --dev
 
 We leverage these data sources to maintain [mappings of which version](https://github.com/babel/babel/blob/master/packages/babel-compat-data/data/plugins.json) of our supported target environments gained support of a JavaScript syntax or browser feature, as well as a mapping of those syntaxes and features to Babel transform plugins and core-js polyfills.
 
-> It is important to note that `@babel/preset-env` does _not_ support `stage-x` plugins.
+> Note: `@babel/preset-env` won't include any JavaScript syntax proposals less than Stage 3 because at that stage in the TC39 process, it wouldn't be implemented by any browsers anyway. Those would need to be included manually. The `shippedProposals` option will include Stage 3 proposals that some browsers have already implemented.
 
 `@babel/preset-env` takes any [target environments you've specified](#targets) and checks them against its mappings to compile a list of plugins and passes it to Babel.