Add custom Don

- Registered users can customise the colour of their Don and it will appear for other players
- Bug fixes:
  - Add lyrics checkbox to admin page
  - 2P shows above "creative" or "with lyrics" labels
  - Prevent accidental alt and menu keyboard presses from triggering browser menus
  - Fixed mouse hitboxes on difficulty selection
  - Clean cached sounds and lyrics when another song is loading
  - Fixed debug jumping to the top-left of the screen when hidden
  - Fixed server volume not being applied to songs

public/src/js/debug.js

@@ -82,6 +82,9 @@ class Debug{
 		}
 	}
 	stopMove(event){
+		if(this.debugDiv.style.display === "none"){
+			return
+		}
 		if(!event || event.type === "resize"){
 			var divPos = this.debugDiv.getBoundingClientRect()
 			var x = divPos.left