This PR is to support overwriting the default `CMD` command of `services` containers.
This is a Gitea specific feature and GitHub Actions doesn't support this syntax.
Reviewed-on: https://gitea.com/gitea/act/pulls/50
Reviewed-by: Jason Song <i@wolfogre.com>
Co-authored-by: Zettat123 <zettat123@gmail.com>
Co-committed-by: Zettat123 <zettat123@gmail.com>