Timed auto concede

[beefsack]

If a player doesn't make plays for a certain amount of time, they automatically concede.

This is more complicated in >2 player games, not 100% sure how to handle that yet. Possibly either counting it as a concede and replacing the player with a bot if bots are available, otherwise it's a tie to the other players (but that's not a good outcome.)

[beefsack]

This issue was moved to Miniand/brdg.me-issues#21