Right-click a website and hit "clean output", and if there's a video element, it will be full windowed.
I've excluded vdo.ninja/invite.cam from this option, since I think it will confuse users to have it there. VDO.Ninja already has clean output options built-in, so this isn't needed.
Once "clean output" is activated, a page refresh will be needed to interact with the page or fix issues. You can mute the window at least, so there's that.