💪 Interactive 6 stack notification

[izzylys]

I'd like to add a message that appears when there is a 6 stack in one of the voice channels to let everyone know that it's full. It should be interactive to allow people to react with an emoji to

1. get notified when someone leaves so they can join in
2. get notified when there are enough people waiting to start a new stack (maybe 3?)

[Killeroo]

From a quick search seems we have some nice events to keep track of stuff:

https://dsharpplus.github.io/api/DSharpPlus.VoiceNext.VoiceNextConnection.html#events

We just need a timer for the notification period, so we don't have these things hanging around forever.