Add a way to toggle off the chat panel in multiplayer rooms

[Ihwa-1]

The leaderboard can be toggled on/off or moved out of the way, but the chat panel can't — it's always there during pauses, before the match starts, and after it ends, with no way to hide it.

Would be nice to get the same treatment chat gets on the leaderboard — a toggle key (like Tab does for the leaderboard) to collapse it when you don't need it, then bring it back whenever. Doesn't need to fully disconnect from chat, just hide the panel visually until toggled back on.

Would help keep the screen cleaner for people who don't need to watch room chat constantly during a lobby.