Implementation of monster-chess

[Cormanz]

This is the initial commit of implementing monster-chess into board-game-rs. All this initial commit does is support Rust in Github codespaces so that I can more easily develop this. There's no progress yet, but I'll be implementing this on the fork and will comment once this is ready for review.

[Cormanz]

board-game-rs's Board implements the following traits: Debug + Display + Clone + Eq + Hash + Send + Sync + UnwindSafe + RefUnwindSafe which are not currently implemented by the monster-chess board and not as easy to implement. I'll have to update monster-chess to implement these traits before further working on the PR (which should hopefully be done soon.)

[KarelPeeters]

I'm also considering just removing some of the bounds from Board;

• Debug and Display are very useful for debugging, so I'm probably keeping those
• Clone is used a lot everywhere, so keeping that
• Eq is used in many of the unit tests, but it probably doesn't need to be a bound on Board.
• Hash can be moved to functions that use caches
• Send and Sync can be moved to the functions that actually do concurrency
• UnwindSafe and RefUnwindSafe should really be removed, I only really use them in unit tests to check that some board functions panic correctly. I should probably use Result a bit more instead, but that can be a bit annoying to use. (eg. for play and available_moves).

[Cormanz]

I'll still make sure to implement Debug + Display + Clone + Eq + Hash + Send + Sync anyways, as it seems like good practice and would perhaps make consumers' lives (like board-game-rs's) easier.

[KarelPeeters]

I've already removed UnwindSafe + RefUnwindSafe (and replaced a bunch of panics with Result), it was not as annoying as I thought.