Attenuation while someone is speaking

[BamButz]

This idea was already mentioned in the issues #161, but it seems that it got lost over the time.
I would like to reintroduce this as it is something that many users on my server are asking for.

[MichailiK]

Hm, 2 things:

1. I believe I tried implementing this a while back, but couldn't find a way to determine when people started/stopped speaking. I can take another look at this though
2. Depending on the ping to the voice region, there's likely gonna be a noticable delay on when JMusicBot's attenuation kicks in & backs off again.

[MichailiK]

Well, looks like past me was quite blind, I've just figured out there is a way to receive audio from users 😅

[MichailiK]

I have an implementation for this at MichailiK@490a077. Unfortunately, there seems to be a bug in JDA 4 which makes the speaking event only fire once, but then never again, no matter how much you start & stop speaking. I believe we'll have to delay this until JMusicBot 0.5.0, where we will switch to JDA 5.