Handle leaving fullscreen with Escape and toggling with F11

[ZimbiX]

Similar to #3, I realised that pressing Escape to leave fullscreen is still slow. I'd forgotten to handle that.

I had a bit of a go, and it seems like neither detecting Escape keydown nor the fullscreenchange event happen soon enough (or at all?). If this is even possible to fix, it's going to be difficult. I'd rather not dive deep into how YouTube's fullscreen toggling works to delay the actual transition.

Handling F11 is related. I haven't tried to do that yet, but I suspect it'll require the same mechanism.

[ZimbiX]

Until this is resolved, I should update the readme to note that only the F key and fullscreen button are currently supported.

Edit: Done

[Metal-spoon]

Escape and f11 are probably never going to be able to be used for this.
You can't override them because they are the panic buttons of fullscreen so to speak.
Only way to do this is to prevent the input and let it press f instead, this can't be done in javascript, one has to use something like AHK to achieve that functionality. Something that runs outside the browser and can capture inputs.
Or modify the code of the browser itself but that is also a stretch.