Add full screen toggle functionality

[ynshung]

Make the shorts full screen by keybind 'F' and the #page-manager will be full-screened. The reason #shorts-container is not full-screened is that the navigation container at the right (go up and down) will not be visible and it doesn't make the video itself bigger than it is.

Credit to #171, closes #187

Future implementation: button on shorts itself

[ynshung]

@adsuth I'm facing the issue where for user with the previous version, when there is a new keybind the 'Key' is completely blank (example image) and the user need to reassign the key:

How do you think we should assign the new key when new versions rolled out?

I also faced another issue for the first time which I couldn't assign it to the 'F' key as it says it's in use, I'm not able to reproduce it again so it probably just a small issue

[adsuth]

Not sure i thought that itd default to "\<disabled>" if it was unpopulated? Maybe do a cursory check if the value is empty, make it disabled?

Busy with uni so i cant give it much time atm unfortunately

edit: it read that as a tag sorry

[ynshung]

Not sure i thought that itd default to "" if it was unpopulated? Maybe do a cursory check if the value is empty, make it disabled?

Busy with uni so i cant give it much time atm unfortunately

Alright thanks for the comment, I'll take a look again when I'm free

Edit: My testing seems to be working now, weird