Disconnect from Lavalink when not in use

[aaronrai24]

• We should probably not remain connected to lava link while not in any active discord voice channels
• When dollar joins a voice channel check if there are any active connections, if not open a new connection(new function)
• When leaving a voice channel, check if dollar is in any other voice channels, if not close the connection else leave it(new function)
• Call these methods in on_voice_state_update