Deploy to GitHub pages

[janhohenheim]

Quote from @rparrett:

Question motivated by my brain, for whatever reason, telling my fingers to type https://thebevyflock.github.io/bevy-template into my address bar and expecting it to work.
IIRC, it was done previously in a PR to bevy_github_ci_template, but that PR also massively reorganized the CI in sort of a controversial way and stalled out.
Seems unimportant for Bevy Jam, but maybe slightly useful for jamming in general.