Hotkey for closing NVil

I'd like to be able to close NVil via alt+F4, so I don't have to drop out of fullscreen mode (with menu hidden) every time. So it would be nice having this command in the tool editor. Maybe those kind of commands deserve their own category. "New Scene" is currently under Common Modelling Shortcut Tools, which is curious, because it has not really anything to do with the actual modelling.

Done.