Merge commit 'be3e8236086165e5e45a5a10783823874b3f3ebd' as 'lib/vscode'

lib/vscode/extensions/css-language-features/CONTRIBUTING.md

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+## Setup
+
+- Clone [microsoft/vscode](https://github.com/microsoft/vscode)
+- Run `yarn` at `/`, this will install
+	- Dependencies for `/extension/css-language-features/`
+	- Dependencies for `/extension/css-language-features/server/`
+	- devDependencies such as `gulp`
+- Open `/extensions/css-language-features/` as the workspace in VS Code
+- Run the [`Launch Extension`](https://github.com/microsoft/vscode/blob/master/extensions/css-language-features/.vscode/launch.json) debug target in the Debug View. This will:
+	- Launch the `preLaunchTask` task to compile the extension
+	- Launch a new VS Code instance with the `css-language-features` extension loaded
+	- You should see a notification saying the development version of `css-language-features` overwrites the bundled version of `css-language-features`
+- Test the behavior of this extension by editing CSS/SCSS/Less files
+- Run `Reload Window` command in the launched instance to reload the extension
+
+### Contribute to vscode-css-languageservice
+
+[microsoft/vscode-css-languageservice](https://github.com/microsoft/vscode-css-languageservice) contains the language smarts for CSS/SCSS/Less.
+This extension wraps the css language service into a Language Server for VS Code.
+If you want to fix CSS/SCSS/Less issues or make improvements, you should make changes at [microsoft/vscode-css-languageservice](https://github.com/microsoft/vscode-css-languageservice).
+
+However, within this extension, you can run a development version of `vscode-css-languageservice` to debug code or test language features interactively:
+
+#### Linking `vscode-css-languageservice` in `css-language-features/server/`
+
+- Clone [microsoft/vscode-css-languageservice](https://github.com/microsoft/vscode-css-languageservice)
+- Run `yarn` in `vscode-css-languageservice`
+- Run `yarn link` in `vscode-css-languageservice`. This will compile and link `vscode-css-languageservice`
+- In `css-language-features/server/`, run `yarn link vscode-css-languageservice`
+
+#### Testing the development version of `vscode-css-languageservice`
+
+- Open both `vscode-css-languageservice` and this extension in a single workspace with [multi-root workspace](https://code.visualstudio.com/docs/editor/multi-root-workspaces) feature
+- Run `yarn watch` in `vscode-css-languageservice` to recompile the extension whenever it changes
+- Run `yarn watch` at `css-language-features/server/` to recompile this extension with the linked version of `vscode-css-languageservice`
+- Make some changes in `vscode-css-languageservice`
+- Now when you run `Launch Extension` debug target, the launched instance will use your development version of `vscode-css-languageservice`. You can interactively test the language features.
+- You can also run the `Debug Extension and Language Server` debug target, which will launch the extension and attach the debugger to the language server. After successful attach, you should be able to hit breakpoints in both `vscode-css-languageservice` and `css-language-features/server/`