[Proposal] Add countdown sounds for watchers

[ch-suginami]

Currently, observers in Lishogi cannot hear sounds indicating the amount of time remaining during a game. In shogi tournaments streamed using Lishogi, the organizer (i.e., the streamer) uses observer mode to explain the board position during the game. In such cases, it would be convenient for observers to hear time-related sounds, as this would allow the streamer and its watchers to keep track of the remaining time. So I will request the addition of a feature that allows observers to hear these sounds.

[WandererXII]

Maybe related - hear opponents clock.

I could add a preference option, something like: Clock sounds I hear: [Only mine] [My and opponent's clock] [Every observed game]