Fullscreen CSS tweak

[richchurcher]

Thanks so much for maintaining this template, I really appreciate it especially the out-of-the-box CI/CD.

I notice that in order to get Itch.io full-screen working correctly (i.e. actually full-screen and not letterboxed) I'm needing to add the following CSS:

canvas#bevy {
    flex-grow: 1;
    z-index: 2;
    height: 100% !important;
    width: 100% !important;
}

Perhaps a trifle hacky, but it does work. I think it may be something to do with the various styles Itch itself injects. Would you accept a PR like this, or is it something you'd prefer folks add after the fact?

Edit: I also needed to add

    height: 100%;
    width: 100%;

to .game-container.

[NiklasEi]

The default should stay as is in my opinion. This way the canvas is not full screen just like the window of default bevy is not full screen.

[richchurcher]

FYI with fit_canvas_to_parent going away, folks will probably need to tweak their CSS in any case: bevyengine/bevy#11057

[NiklasEi]

The option will likely be back with the next version, see bevyengine/bevy#11278
I am tracking in #104

[richchurcher]

Oh, nice. Yeah, that seems better TBH.