Implement FullScreen & Mobile Controls for the Iframe Embed

[torch2424]

relates to #320

The fullscreen button should just be in the control bar, and set the emulator to take the full screen, preserving the gameboy aspect ratio (160 x 144).

Mobile Controls UX will be difficult. Since, it is not possible to detect reliably if you are on a small device within an iframe. Need to find a way to make a mobile controls toggle that is obvious, but at the same time, not always visible obstructing the game view 🤔

[torch2424]

Here's one okay example: https://oldgameshelf.com/, But they just use the host site and show the controls upfront outside of their frame.

[torch2424]

We can do something similar to: https://www.retrogames.cc/

Let's show the mobile controls by default. but add a toggle button in the control bar at the bottom of the page. This way, it's super easy for desktop users to just turn it off, and mobile users will know they can play 😄