docs(CONTRIBUTING.md): fix some typos (#4917)

As someone who's new to the project, I read the contributing guide and spotted some things that confused me. Hopefully this patch helps to reduces the confusion for others!

CONTRIBUTING.md

@@ -12,8 +12,8 @@
   * [Public API Coverage](#public-api-coverage)
   * [Debugging Puppeteer](#debugging-puppeteer)
 - [For Project Maintainers](#for-project-maintainers)
-  * [Releasing to NPM](#releasing-to-npm)
+  * [Releasing to npm](#releasing-to-npm)
-  * [Updating NPM dist tags](#updating-npm-dist-tags)
+  * [Updating npm dist tags](#updating-npm-dist-tags)
 <!-- gen:stop -->
 
 # How to Contribute
@@ -76,6 +76,7 @@ npm run lint
 ## API guidelines
 
 When authoring new API methods, consider the following:
+
 - Expose as little information as needed. When in doubt, don’t expose new information.
 - Methods are used in favor of getters/setters.
   - The only exception is namespaces, e.g. `page.keyboard` and `page.coverage`
@@ -123,9 +124,9 @@ To deliver to a different location, use "deliver" option:
 
 ## Writing Documentation
 
-All public API should have a descriptive entry in the [docs/api.md](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md). There's a [documentation linter](https://github.com/GoogleChrome/puppeteer/tree/master/utils/doclint) which makes sure documentation is aligned with the codebase.
+All public API should have a descriptive entry in [`docs/api.md`](https://github.com/GoogleChrome/puppeteer/blob/master/docs/api.md). There's a [documentation linter](https://github.com/GoogleChrome/puppeteer/tree/master/utils/doclint) which makes sure documentation is aligned with the codebase.
 
-To run documentation linter, use:
+To run the documentation linter, use:
 
 ```bash
 npm run doc
@@ -147,7 +148,7 @@ A barrier for introducing new installation dependencies is especially high:
 - Tests should be *hermetic*. Tests should not depend on external services.
 - Tests should work on all three platforms: Mac, Linux and Win. This is especially important for screenshot tests.
 
-Puppeteer tests are located in [test/test.js](https://github.com/GoogleChrome/puppeteer/blob/master/test/test.js)
+Puppeteer tests are located in [`test/test.js`](https://github.com/GoogleChrome/puppeteer/blob/master/test/test.js)
 and are written with a [TestRunner](https://github.com/GoogleChrome/puppeteer/tree/master/utils/testrunner) framework.
 Despite being named 'unit', these are integration tests, making sure public API methods and events work as expected.
 
@@ -178,7 +179,7 @@ npm run unit -- --break-on-failure
   fit('should work', async function({server, page}) {
     const response = await page.goto(server.EMPTY_PAGE);
     expect(response.ok).toBe(true);
-  })
+  });
 ```
 
 - To disable a specific test, substitute the `it` with `xit` (mnemonic rule: '*cross it*'):
@@ -189,7 +190,7 @@ npm run unit -- --break-on-failure
   xit('should work', async function({server, page}) {
     const response = await page.goto(server.EMPTY_PAGE);
     expect(response.ok).toBe(true);
-  })
+  });
 ```
 
 - To run tests in non-headless mode:
@@ -218,7 +219,7 @@ node --inspect-brk test/test.js
 
 ## Public API Coverage
 
-Every public API method or event should be called at least once in tests. To ensure this, there's a coverage command which tracks calls to public API and reports back if some methods/events were not called.
+Every public API method or event should be called at least once in tests. To ensure this, there's a `coverage` command which tracks calls to public API and reports back if some methods/events were not called.
 
 Run coverage:
 
@@ -232,42 +233,44 @@ See [Debugging Tips](README.md#debugging-tips) in the readme.
 
 # For Project Maintainers
 
-## Releasing to NPM
+## Releasing to npm
+
+Releasing to npm consists of the following phases:
 
-Releasing to NPM consists of 3 phases:
 1. Source Code: mark a release.
     1. Bump `package.json` version following the SEMVER rules and send a PR titled `'chore: mark version vXXX.YYY.ZZZ'` ([example](https://github.com/GoogleChrome/puppeteer/commit/808bf8e5582482a1d849ff22a51e52024810905c)).
     2. Make sure the PR passes **all checks**.
         - **WHY**: there are linters in place that help to avoid unnecessary errors, e.g. [like this](https://github.com/GoogleChrome/puppeteer/pull/2446)
     3. Merge the PR.
     4. Once merged, publish release notes using the "create new tag" option.
-        - **NOTE**: tag names are prefixed with `'v'`, e.g. for version `1.4.0` tag is `v1.4.0`.
+        - **NOTE**: tag names are prefixed with `'v'`, e.g. for version `1.4.0` the tag is `v1.4.0`.
-2. Publish `puppeteer` to NPM.
+2. Publish `puppeteer` to npm.
     1. On your local machine, pull from [upstream](https://github.com/GoogleChrome/puppeteer) and make sure the last commit is the one just merged.
     2. Run `git status` and make sure there are no untracked files.
-        - **WHY**: this is to avoid bundling unnecessary files to NPM package
+        - **WHY**: this is to avoid adding unnecessary files to the npm package.
     3. Run [`pkgfiles`](https://www.npmjs.com/package/pkgfiles) to make sure you don't publish anything unnecessary.
-    4. Run `npm publish`. This will publish `puppeteer` package.
+    4. Run `npm publish`. This publishes the `puppeteer` package.
-3. Publish `puppeteer-core` to NPM.
+3. Publish `puppeteer-core` to npm.
-    1. Run `./utils/prepare_puppeteer_core.js`. The script will change the name inside `package.json` to `puppeteer-core`.
+    1. Run `./utils/prepare_puppeteer_core.js`. The script changes the name inside `package.json` to `puppeteer-core`.
-    2. Run `npm publish`. This will publish `puppeteer-core` package.
+    2. Run `npm publish`. This publishes the `puppeteer-core` package.
     3. Run `git reset --hard` to reset the changes to `package.json`.
 4. Source Code: mark post-release.
     1. Bump `package.json` version to `-post` version and send a PR titled `'chore: bump version to vXXX.YYY.ZZZ-post'` ([example](https://github.com/GoogleChrome/puppeteer/commit/d02440d1eac98028e29f4e1cf55413062a259156))
         - **NOTE**: make sure to update the "released APIs" section in the top of `docs/api.md`.
         - **NOTE**: no other commits should be landed in-between release commit and bump commit.
 
-## Updating NPM dist tags
+## Updating npm dist tags
 
-For both `puppeteer` and `puppeteer-firefox` we maintain the following NPM Tags:
+For both `puppeteer` and `puppeteer-core` we maintain the following npm tags:
-- `chrome-*` tags, e.g. `chrome-75` and so on. These tags match Puppeteer version that corresponds to the `chrome-*` release.
+
-- `chrome-stable` tag. This tag points to the Puppeteer version that works with current Chrome stable.
+- `chrome-*` tags, e.g. `chrome-75` and so on. These tags match the Puppeteer version that corresponds to the `chrome-*` release.
+- `chrome-stable` tag. This tag points to the Puppeteer version that works with the current Chrome stable release.
 
 These tags are updated on every Puppeteer release.
 
 > **NOTE**: due to Chrome's rolling release, we take [omahaproxy's linux stable version](https://omahaproxy.appspot.com/) as *stable*.
 
-Manging tags 101:
+Managing tags 101:
 
 ```bash
 # list tags