Add itch.io page for testing the upload of this repo itself

[benfrankel]

This may be incompatible with https://github.com/TheBevyFlock/bevy-template/issues/1.

[Sapein]

This may be incompatible with #1.

Assuming this would run in CI, we could just use cargo-generate to create the CI version that we're testing.

Edited to add: You can also use cargo-generate on local directories as well. So we can just use that in setting that up.

[benfrankel]

True, but then the CI would be wrong for the user?

There may be a way around this. IMO these are 2 important / useful features to support, so if a bit of a hack is needed to support both, it's worth it.

[benfrankel]

Unsure which user should create the itch.io page. There can be multiple admins, but only one owner, whose username also becomes part of the URL.

[janhohenheim]

I'd create a new user.

[benfrankel]

We now have https://the-bevy-flock.itch.io/bevy-template, so this issue is unblocked :)

[benfrankel]

Release workflow is functioning now, although the web release is broken because of web/index.html. Technically that's a separate issue, though: There is an itch.io page, and our broken game is uploaded to it automatically :tada:

EDIT: And web build is now functional.