Alternative ideas to remind users to submit review

Following up from !92044 (comment 1069018216)

Some ideas:

UI changes

• Add background color to Submit review bar
• Animate Submit review button when a user starts a review
• Move Submit review to more obvious location (maybe the top somewhere)
  • This will be easier after the MR restructure

Notify users

• Generate todo if user leaves review
• Send email if review hasn't been submitted in a certain amount of time
• Alert user if they remove themselves as reviewer without submitting their review