deploy gitlab pages with the right baseURL
Hugo requires some baseURL setting. By default it's /
which breaks
the site when deployed in a subpath, like when we deploy in gitlab
pages.
So, instead of reusing the CI template, we just vendor the code in here and build hugo for pages specially. We can still have a more "standard" staging as that will work because it's published at the root, but at least pages will work now.
See: #15