[Feature Request] Add whisper support to multiple channels

[DuckBoss]

Also, if I may do so here: I'd like to request the bot to be able to be active in several channels at the same time, for example have it in the master channel and also sound in sub-channels. but that is a request for later :)

This is a request by @gymnae in a different issue post, which I decided to make into a separate feature request so it's easier to keep track of.

[DuckBoss]

Update: There is currently no mumble library support for whispering to multiple channels, so implementing this for the bot would require assignment of whisper users within the individual channels, and use callbacks to detect when a user is no longer part of the channel. This would require a significant restructuring of the current whisper implementation in the bot.