Add some documentation to play_mp3
Add some documentation to play_mp3

VxJasonxV/discordrb,Roughsketch/discordrb,VxJasonxV/discordrb,meew0/discordrb,megumisonoda/discordrb,megumisonoda/discordrb,Roughsketch/discordrb,meew0/discordrb