Use galaxy.yml to figure out the right API call

[GregSutcliffe]

Rather than assuming x.y format from the repo name, we could use galaxy.yml from the repo.

Would need an extra GET from GitHub (since we don't clone the repos for this tool), but that should be fairly fast if we get the raw file. However, raw files contain the primary branch name (https://raw.githubusercontent.com/ansible-collections/community.general/main/galaxy.yml), so we'd have to figure that out too.

cc @gundalow thanks for the idea :)

[GregSutcliffe]

As per #25 we probably want to move to using GH tags for this - although that means we can't easily quantify non-GH repos (e.g. openstack) and I'm not sure it helps with multi-collection repos like pure. We may need some hand-written config in the crawler...