Code Review Feature

[sestinj]

This PR adds

• dedicated UI in the sidebar for code review
• logic for watching over the git diff of current working changes and triggering review at a reasonable schedule
• basic prompts for review
• configuration options to customize review

Currently the biggest thing holding this back from merging is the quality of the prompts. We want to ensure that the LLM can return specific results, without outputting too much random discussion. It should give a clear "yes/no" depending on whether the review passed, which can be used to display either a green checkmark or red x in the UI