Make it possible to define custom site directory within artifacts for GitLab Pages
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 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?