add 'saveKeys' boolean to GameType.game_type, which should tell us to assign the new userKeys record to the InputState (which is implemented), and should also tell us to convert the keys to a string and save it to controls.config

fcore/game-update.sml

@@ -4,7 +4,7 @@ struct
 
   fun update (game: GameType.game_type, input, time) =
     let
-      val {mode, userKeys} = game
+      val {mode, userKeys, saveKeys = _} = game
     in
       case mode of
         LEVEL level => LevelUpdate.update (level, input, userKeys, time)