Rapid React: JSON storage

This is a low-priority issue; the production scouting website uses SQLite, and if I can find people who are willing to learn/be taught SQL I'll probably deprecate the JSON storage system anyway. However, if someone's looking for a project to get more familiar with the scouting library codebase, you could implement a class `RapidReactJSON implements JSONStoragePlan`. (As with SQLite, looking at Infinite Recharge should give you an idea of how it should be done.)

Start by locating the existing JSONStoragePlan implementations and the Infinite Recharge storage code, then compare their handling of RapidReactMatch data with the SQLite approach mentioned in the issue. Implement the RapidReactJSON class to match the existing storage interface; done means the Rapid React JSON storage backend is consistent with the established pattern.

Written by the indexing model from the issue text.