Update docs to include PR review approval specification

[d33bs]

Description

This PR adds documentation about pull request review approval expectations to help abide #43 and inform contributors about how this project works. After approval of this PR I plan to enable branch protection rules for the repository which will require at least one approving pull request review in order for work to be merged.

Thank you for any feedback or input on this!

Fixes # (link issue)

References #43 (I'll close the issue after the work for branch protection is completed)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

n/a

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• Existing tests pass locally with my changes
• I have written new tests that prove my fix is effective or that my feature works
• I have commented my code, particularly in hard-to-understand areas
• I have linted my code locally before submission
• Any dependent changes have been merged and published in downstream modules
• I have added an explanation of what my changes do and why I'd like them to be include
• I have checked to ensure there aren't other open Pull Requests for the same update/change?