Issue

Currently when using this on gitea.com:

- uses: actions/setup-python@v4

It will resolve to instance-specific URL https://gitea.com/actions/setup-python which I see very problematic because it makes action names ambigous across multiple gitea instances and github itself (where this will work).

Proposal

If the action URL is not absolute, assume a hardcoded https://github.com/ prefix, just like podman and docker assume a docker.io/ prefix on images not having a fully qualified name. This will ensure that action names are unambigously resolvable globally.