Add new game fields (#12)

Add width, height and chatId to game.

Author: marein

go/connectfour/v1/messaging.pb.go

@@ -78,4 +78,7 @@ message Game {
   string yellow_player_id = 3;
   string current_player_id = 4;
   repeated Move moves = 5;
+  int32 width = 6;
+  int32 height = 7;
+  string chat_id = 8;
 }