[gamemode.ini] Add renice information about the user group.

example/gamemode.ini

@@ -23,6 +23,8 @@ softrealtime=off
 
 ; GameMode can renice game processes. You can put any value between 0 and 20 here, the value
 ; will be negated and applied as a nice value (0 means no change). Defaults to 0.
+; To use this feature, the user must be added to the gamemode group (and then rebooted):
+; sudo usermod -aG gamemode $(whoami)
 renice=0
 
 ; By default, GameMode adjusts the iopriority of clients to BE/0, you can put any value