[Feature Request] Add the game management system (GMS)

[wanjohiryan]

This will be the back bone of how Nestri works, currently we require the user to download and install the game themselves, plus do a bunch of wizardly to run the game inside the Nestri docker container.

And in the spirit of rebranding, we want to make this step much easier and more straight-forward.

So here are the proposed steps for this "new" gaming:

• Login to your game store of choice -
  • Let us start with Epic Game Store as it already has an open-source cmd equivalent for it
• Download the chosen game. The user can only chose one game, only one for now, and we download and cache it. Using legendary
• Set up Wine or Proton using JS, replace the nestri-proton bash script with a binary written in JavaScript
• Set up game cloud sync on user exit

...more?