✨ Code Review Ribbon

A code review ribbon needs to exist in the ruler view that both indicates change and provides actions the user can take on these changes including:
- Show Change - which will show the user the original code before the change above
- Discarding Change - which will remove the changed code and replace it with what existed before the change

See below screenshots to see how this might look (or refer to Xcode for reference)

Note: This may require #127 to be complete in order to begin working on this.