docs(contributing): refactor & formatting

.github/CONTRIBUTING.md

@@ -32,7 +32,7 @@ In case you are suggesting a new feature, we will match your idea with our curre
 * Fork the **webpack-cli** repo at [https://github.com/webpack/webpack-cli](https://github.com/webpack/webpack-cli).
 * `git clone <your-clone-url> && cd webpack-cli`
 
-### Setup with npm
+### Using npm
 
 * Install the dependencies and link them:
 
@@ -49,68 +49,81 @@ In case you are suggesting a new feature, we will match your idea with our curre
   npm run build
   ```
 
-* Run all the tests with:
+### Using yarn
+
+* If you don't have yarn yet: 
 
   ```bash
-  npm run test
+  npm install -g yarn
   ```
-
-* To test a single CLI (flag) test case:
 
+* Install the dependencies and link them
+
   ```bash
-  BIN_TEST_CASES_GREP=/myCase jest test/BinTestCases.test.js`
+  yarn
+  yarn link
+  yarn link webpack-cli
   ```
 
-* To test a single CLI (other type of) test case:
-  - `npx jest path/to/my-test.js` 
-  - You can also install jest globally and run tests without npx:
-    - `npm i -g jest`
-  - If you have jest installed globally:
-    - `jest path/to/my-test.js`
+* Bootstrap all the submodules before building for the first time
 
-* To test linting:
   ```bash
-  npm run lint && npm run tslint
+  yarn bootstrap
+  yarn build
   ```
 
-### Setup with yarn
-* If you don't have yarn yet: 
+
+## Testing
+
+### Using npm
+
+* Run all the tests with:
 
   ```bash
-  npm install -g yarn
+  npm run test
   ```
+
+* Test a single CLI test case:
 
-* Install the dependencies and link them
+  ```bash
+  npx jest path/to/my-test.js 
+  ```
+
+* You can also install jest globally and run tests without npx:
 
   ```bash
-  yarn
-  yarn link
-  yarn link webpack-cli
+  npm i -g jest
+  jest path/to/my-test.js
   ```
 
-* Bootstrap all the submodules before building for the first time
+* You can run the linters:
 
   ```bash
-  yarn bootstrap
-  yarn build
+  npm run lint && npm run tslint
   ```
 
+### Using yarn
+
 * Run all the tests with:
 
   ```bash
   yarn test
   ```
 
-* To test a single CLI (flag) test case:
+* Test a single CLI test case:
 
   ```bash
-  BIN_TEST_CASES_GREP=/myCase jest test/BinTestCases.test.js
+  yarn jest path/to/my-test.js
   ```
+
+* You can also install jest globally and run tests:
 
-* To test a single CLI (other type of) test case:
-    - `yarn jest path/to/my-test.js`
+  ```bash
+  yarn global add jest
+  jest path/to/my-test.js
+  ```
 
-* To test linting:
+* You can run the linters:
 
   ```bash
   yarn lint && yarn tslint