New option to limit Undo window

By default, you have an unlimited amount of time to undo a move until the opponent makes their next move. There’s a new option now when creating a game where you can impose a time limit on Undos or requests-to-undo (if you have the option enabled where you need the opponent’s permission). If you have this enabled, you’ll see a little clock on the Undo button after making a move, and once the time has expired, you’re committed to that move and can no longer Undo or request an Undo.