Add functionality to useFullScreen to determine if fullscreen is supported in your environment

[pjjanak]

Description

Right now the only thing I can see missing from useFullScreen is the ability to check if fullscreen is even allowed/enabled by the browser an app is being rendered in.

Suggested implementation

useFullScreen can be modified to export a boolean enabled which would be:

document.fullscreenEnabled || document.webkitFullscreenEnabled || document.mozFullScreenEnabled || document.msFullScreenEnabled