docs: add CONTRIBUTING.md (#589)

* docs: add CONTRIBUTING.md

* docs: update contribution link in README

* Update CONTRIBUTING.md

.github/CONTRIBUTING.md

@@ -0,0 +1,93 @@
+# Vue Test Utils Contributing Guide
+
+Hi! I’m really excited that you are interested in contributing to Vue Test Utils. Before submitting your contribution though, please make sure to take a moment and read through the following guidelines.
+
+- [Code of Conduct](https://github.com/vuejs/vue/blob/dev/.github/CODE_OF_CONDUCT.md)
+- [Issue Reporting Guidelines](#issue-reporting-guidelines)
+- [Pull Request Guidelines](#pull-request-guidelines)
+- [Development Setup](#development-setup)
+- [Project Structure](#project-structure)
+
+## Issue Reporting Guidelines
+
+- Always use [https://new-issue.vuejs.org/](https://new-issue.vuejs.org/) to create new issues.
+
+## Pull Request Guidelines
+
+- The `master` branch is basically just a snapshot of the latest stable release. All development should be done in dedicated branches. **Do not submit PRs against the `master` branch.**
+
+- Checkout a topic branch from the relevant branch, e.g. `dev`, and merge back against that branch.
+
+- Work in the `src` folder and **DO NOT** checkin `dist` in the commits.
+
+- It's OK to have multiple small commits as you work on the PR - we will let GitHub automatically squash it before merging.
+
+- Make sure `npm test` passes. (see [development setup](#development-setup))
+
+- If adding new feature:
+  - Add accompanying test case.
+  - Provide convincing reason to add this feature. Ideally you should open a suggestion issue first and have it greenlighted before working on it.
+
+- If fixing a bug:
+  - If you are resolving a special issue, add `(fix #xxxx[,#xxx])` (#xxxx is the issue id) in your PR title for a better release log, e.g. `update entities encoding/decoding (fix #3899)`.
+  - Provide detailed description of the bug in the PR. Live demo preferred.
+  - Add appropriate test coverage if applicable.
+
+## Development Setup
+
+You will need [Node.js](http://nodejs.org) **version 6+**
+
+Vue Test Utils is a monorepo. It contains a root package.json for running scripts across the project. The code is inside sepearte packages in the `packages` directory. The project uses [lerna](https://lernajs.io/) to manage the workspaces.
+
+After cloning the repo, run:
+
+``` bash
+$ yarn
+```
+
+Or with npm:
+
+```bash
+npm i && npm run bootstrap
+```
+### Commonly used NPM scripts
+
+``` bash
+# run unit tests with mocha-webpack
+$ npm run test:unit
+
+# run the full test suite, include linting / type checking
+$ npm test
+```
+
+There are some other scripts available in the `scripts` section of the `package.json` file.
+
+The default test script will do the following: lint with ESLint -> type check with Flow -> unit tests. **Please make sure to have this pass successfully before submitting a PR.** Although the same tests will be run against your PR on the CI server, it is better to have it working locally beforehand.
+
+## Project Structure
+
+- **`docs`**: contains files used to generate https://vue-test-utils.vuejs.org/ with [GitBook](https://www.gitbook.com/).
+
+- **`flow`**: contains type declarations for [Flow](https://flowtype.org/). These declarations are loaded **globally** and you will see them used in type annotations in normal source code.
+
+- **`packages`**: contains the `test-utils` and `server-test-utils` public packages. Also contains private packages `shared` and `create-instance` wich are used by `test-utils` and `server-test-utils`. The codebase is written in ES2015 with [Flow](https://flowtype.org/) type annotations.
+
+  - **`test-utils`**: the @vue/test-utils package.
+
+    - **`dist`**: contains built files for distribution. Note this directory is only updated when a release happens; they do not reflect the latest changes in development branches.
+
+  - **`server-test-utils`**: the @vue/server-test-utils package
+
+    - **`dist`**: contains built files for distribution. Note this directory is only updated when a release happens; they do not reflect the latest changes in development branches.
+
+  - **`create-instance`**: private package that creates an instance and applies mounting options. 
+
+  - **`shared`**: private package that contains utilities used by the other packzges.
+
+- **`scripts`**: contains build-related scripts and configuration files. In most cases you don't need to touch them. 
+
+- **`test`**: contains all tests. The unit tests are written with [Mocha](https://mochajs.org/) and run with [Karma](http://karma-runner.github.io/0.13/index.html) and [mocha-webpack](http://zinserjan.github.io/mocha-webpack/), which compiles the code with webpack before running it in mocha.
+
+- **`types`**: contains TypeScript type definitions
+
+    - **`test`**: type definitions tests

README.md

@@ -43,7 +43,7 @@ Please make sure to read the [Issue Reporting Checklist](https://github.com/vuej
 
 ## Contribution
 
-Please make sure to read the [Contributing Guide](https://github.com/vuejs/vue/blob/dev/.github/CONTRIBUTING.md) before making a pull request.
+Please make sure to read the [Contributing Guide](https://github.com/vuejs/vue-test-utils/blob/dev/.github/CONTRIBUTING.md) before making a pull request.
 
 ## Changelog