pipeline: accept other git hosts than GitHub e.g. GitLab

[graphicore]

Some projects don't host their font project repositories originally on GitHub. E.g. SMC host on GitLab and merely mirror to GitHub. Hence, the projects live on GitLab, so do issue trackers etc. I wonder if we should accept other hosts for projects. This could make tooling more complicated when automation expects the GitHub API to be available, e.g. could be when downloading attachments from tag releases (I'll file an issue for this in googlefonts/gftools#230).

For an introduction see also googlefonts/gftools#231

If we have a https:// url to the git repository, that works with git clone, this actually works already in gftools packager e.g. in upstream.yaml

repository_url: https://github.com/smc/Chilanka.git

can also be

repository_url: https://gitlab.com/smc/fonts/chilanka.git

and the result will be the same.