So far, most of the AI code review tools I've seen in the wild have been pretty lackluster. I figure we should give the new Gemini Code Assist variant a try: https://github.com/marketplace/gemini-code-assist/. This PR adds an initial yaml config for it. Relevant commands (as comments on the OP PR): * `/gemini review` to perform a code review * `/gemini summary` provides a code summary * comment like normal tagging `@gemini-code-assist` * `/gemini help`