Currently GitLab Pages can be only deployed when artifacts repository contains a `public/` directory. It would be nice to make it possible to configure this directory, since someone may want to use pages with existing project, and `public/` directory is often already there. Like in GitLab, we have a [public](public) directory already taken, and this is quite common name. Maybe it would be easy to use the first directory in artifacts and raise error if there is more than one? /cc @ayufan @JobV