Volume control

[meew0]

discord.js added the ability to control the bot's volume, and it would be nice if this was implemented into Lethe as a command. However, this was implemented after the ffmpeg changes and so this will require #27 to be fixed first.

[TehSeph]

Volume is also only set on stream creation, so it would need to be an additional argument for an existing command not a new command.

[meew0]

I'd still rather make it a public value that gets set by a command (and then applies to future plays), because queueing and playing may occur at very different times, and if possible I'd avoid any other arguments to yt because they'd have to go at the start (they could be part of a saved name if they're at the end) and that just leads to confusion.

[meew0]

I'm still debating whether Lethe actually needs this because users can just set the volume on their end, but I suppose server owners would want to turn it down.

[FFZendikar]

To add onto this, even setting volume at 0% is still high for my users.

[macdja38]

to add onto this @FFZendikar have them lower their master volume in discord. if it's at 100% then setting something's volume to 0 makes it actually 0.