Allow keeping screen on when locking screen.
Since GNOME now uses GDM for screen locking I think this is the correct place. Apologies if it isn't.
I often use my laptop to play music over an HDMI connection. This works well, however I want to leave my computer alone locked. However when I lock the screen it turns off the display, causing the music to stop. Jiggling the mouse, or typing half a password only keeps the screen alive for a short period of time.
It would be great if there was an option or toggle to keep a display on forever even when the screen is locked.