Update links to getting started section

docs/contributors/coding-guidelines.md

@@ -201,6 +201,6 @@ alert( `My name is ${ name }.` );
 We use
 [`phpcs` (PHP\_CodeSniffer)](https://github.com/squizlabs/PHP_CodeSniffer) with the [WordPress Coding Standards ruleset](https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards) to run a lot of automated checks against all PHP code in this project.  This ensures that we are consistent with WordPress PHP coding standards.
 
-The easiest way to use PHPCS is [local environment](https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md#local-environment). Once that's installed, you can check your PHP by running `npm run lint-php`.
+The easiest way to use PHPCS is [local environment](/docs/contributors/getting-started.md#local-environment). Once that's installed, you can check your PHP by running `npm run lint-php`.
 
 If you prefer to install PHPCS locally, you should use `composer`. [Install `composer`](https://getcomposer.org/download/) on your computer, then run `composer install`.  This will install `phpcs` and `WordPress-Coding-Standards` which you can the run via `vendor/bin/phpcs`.

docs/contributors/testing-overview.md

@@ -21,7 +21,7 @@ When writing tests consider the following:
 
 Tests for JavaScript use [Jest](https://jestjs.io/) as the test runner and its API for [globals](https://jestjs.io/docs/en/api.html) (`describe`, `test`, `beforeEach` and so on) [assertions](https://jestjs.io/docs/en/expect.html), [mocks](https://jestjs.io/docs/en/mock-functions.html), [spies](https://jestjs.io/docs/en/jest-object.html#jestspyonobject-methodname) and [mock functions](https://jestjs.io/docs/en/mock-function-api.html). If needed, you can also use [Enzyme](https://github.com/airbnb/enzyme) for React component testing.
 
-Assuming you've followed the [instructions](https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md) to install Node and project dependencies, tests can be run from the command-line with NPM:
+Assuming you've followed the [instructions](/docs/contributors/getting-started.md) to install Node and project dependencies, tests can be run from the command-line with NPM:
 
 ```
 npm test
@@ -344,7 +344,7 @@ It's tempting to snapshot deep renders, but that makes for huge snapshots. Addit
 
 ## End to end Testing
 
-If you're using the built-in [local environment](https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md#local-environment), you can run the e2e tests locally using this command:
+If you're using the built-in [local environment](/docs/contributors/getting-started.md#local-environment), you can run the e2e tests locally using this command:
 
 ```bash
 npm run test-e2e
@@ -370,7 +370,7 @@ WP_BASE_URL=http://localhost:8888 WP_USERNAME=admin WP_PASSWORD=password npm run
 
 ## PHP Testing
 
-Tests for PHP use [PHPUnit](https://phpunit.de/) as the testing framework. If you're using the built-in [local environment](https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md#local-environment), you can run the PHP tests locally using this command:
+Tests for PHP use [PHPUnit](https://phpunit.de/) as the testing framework. If you're using the built-in [local environment](/docs/contributors/getting-started.md#local-environment), you can run the PHP tests locally using this command:
 
 ```bash
 npm run test-php

docs/designers-developers/developers/tutorials/javascript/js-build-setup.md

@@ -2,7 +2,7 @@
 
 This page covers how to set up your development environment to use the ESNext and [JSX](https://reactjs.org/docs/introducing-jsx.html) syntaxes. ESNext is JavaScript code written using features that are only available in a specification greater than ECMAScript 5 (ES5 for short). JSX is a custom syntax extension to JavaScript which helps you to describe what the UI should look like.
 
-This documentation covers development for your plugin to work with Gutenberg. If you want to setup a development environment for developing Gutenberg itself, see the [CONTRIBUTING.md](https://github.com/WordPress/gutenberg/blob/master/CONTRIBUTING.md) documentation.
+This documentation covers development for your plugin to work with Gutenberg. If you want to setup a development environment for developing Gutenberg itself, see the [Getting Started](/docs/contributors/getting-started.md) documentation.
 
 Most browsers can not interpret or run ESNext and JSX syntaxes, so we use a transformation step to convert these syntaxes to code that browsers can understand.