HTML5 Full Screen Extension

Demo instructions: run it and move the character. You'll see a grey "Fullscreen button" on the bottom right. Click it to enter full screen. While on fullscreen, click on the button again to exit back to windowed mode. As you probably know, window_set_fullscreen() does not work on HTML5. So  after searching online, I basically copy/pasted a small Javascript code for a GMS1 extension found in this f…