Add Ctrl+Q as a shortcut for closing on linux

[WeaverSong]

Extremely minor qol. Ctrl+Q is a standard shortcut for closing applications on linux, and adding it would help streamline workflow for linux users.

[Mew Pur Pur]

Approved, I'll add this right now.

[Kiisu_Master]

Doesn't need to be Linux only, it's used in many apps on any platform.

[Mew Pur Pur]

Resolved by #717