Creating Contribution Guide (#644)

This merge is a test to see if Lighthouse CI is being honest to us or not

Co-authored-by: dorian451 <[email protected]>

Author: DarknessUnder

docs/contributing/how_to_review.md

@@ -0,0 +1,13 @@
+# How to Review a Pull Request
+
+1. Find  a pull request.
+2. Find the name of the branch in the pull request:
+   * ![showing name of a pull request](img/pull_request_name.png)
+   * In this case, the branch name would be `contributing_guide`.
+3. Open a terminal and navigate to your local repository (the `yacs.n` folder)
+4. Make sure your computer's repo is up to date by running `git pull`.
+5. Run `git switch <branch name>`.
+6. On some computers, if you are running the local version of YACS already, it will update automatically. If it doesn't, restart Docker and refresh the localhost page.
+7. Look at the pull request and verify that whatever functionality it adds works and doesn't seem to cause any problems. 
+8. Add your review (whether it's an approval or not) hitting the "add your review" button:
+   * ![add your review](img/add_review.png)