It might be useful for those self-hosting a Codeberg Pages instance to be able to serve a different error page than the one embedded with go:embed
Reviewed-on: https://codeberg.org/Codeberg/pages-server/pulls/393
Co-authored-by: Gnarwhal <git.aspect893@passmail.net>
Co-committed-by: Gnarwhal <git.aspect893@passmail.net>