add: mpd volume info

.config/i3blocks/config

@@ -4,10 +4,14 @@ align=center
 separator=false
 separator_block_width=15
 
-[status_mpd]
-command=./mpc-status
+[mpd_current]
+command=./mpc-current
 interval=persist
 
+[mpd_volume]
+command=mpc volume | cut -d ":" -f 2
+interval=1
+
 [open_ncmpcpp]
 full_text=♪
 command=i3-msg exec "alacritty -e ncmpcpp" > /dev/null