Code Review Lesson PR

@nkorinek

Description

Adds a lesson on code review, including required images

Fixes #1042

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• The lesson is now accessible in the table of contents for the GitHub chapter of the intro course (served website locally)
• domain/courses/intro-to-earth-data-science/git-github/github-collaboration/how-to-review-code-on-github/ leads to the new page

Checklist:

• I have already submitted an issue and i was invited to submit a pr by an earthdatascience.org maintainer
• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings