Implement a basic URL scheme.

[adityaruplaha]

Fixes #307.

Implementation based on what I read here:
electron-userland/electron-builder#4035
electron/electron#4857

Scheme is a lot like HTTP, except that there's no domain name.
Like heroic://launch?appName=Hazelnut.

[flavioislima]

Maybe to test you just need to put
open heroic://
on the terminal
or xdg-open, like we are doing with the urls to open the epic login page.

[adityaruplaha]

Done. Should work perfectly.

Everything is broken. Fml.

[adityaruplaha]

@flavioislima this is ready to be merged, but problem is that the frontend has no idea what just happened. I'll make the backend state-aware and the client can just query it. Would also reduce the global state.

That'll might have to be a seperate PR tho.

[flavioislima]

Looks good. I'm just not 100% on the user confirmation because if the desktop file will be clicked, then I think it was on porpuse. Steam and lutris don't ask for confirmation for instance. So I think this might not be necessary. But merge it and we can think about that before release.

[adityaruplaha]

I'm just not 100% on the user confirmation

I'm not either, but I did it just in case as its easier to remove something than to implement it pre-release.