Multiplayer progress!

Movement!

As you can see, multiplayer movement is (sort of) working! There are still one or two bugs to iron out, but it's mostly working. Once those bugs are ironed out, I'm going to be working on a main menu, lobbies, client prediction and server rollback, before implementing back guns, elevators, explosive barrels, etc.

Quite a short update, but there isn't that much to share.