Add Github Action for Ansible Galaxy release

This PR adds a workflow for releases.

This still needs:

@displague please log in to https://galaxy.ansible.com/accounts/login/ with Equinix creadentials and create collection equinix.cloud
acquire GALAXY_TOKEN that can add releases to the equinix.cloud collection
Add GALAXY_TOKEN to the METAL_API_TOKEN Gtihub Actions env (and maybe consider renaming the METAL_API_TOKEN env)

Anyway, this is one of the things that we won't know if it works until we try.

equinix-labs / ansible-collection-equinix