ci(ui): Add GitHub workflow to regenerate static assets

Add a GitHub workflow to regenerate and commit the static assets posting a specific comment in a PR, something like `/generate-static-assets`.

_Originally posted by @TwiN in https://github.com/TwiN/gatus/issues/1408#issuecomment-3667506446_

Maybe we can use the [github/command](https://github.com/github/command) action as showcased [here](https://issue-ops.github.io/docs/setup/comment-workflow).