Going for binderhub 1.0.0, we should have clear release documentation as well

• PyPI trusted releases (see Publish to PyPI from a github workflow by declaring the workflow to be trusted team-compass#648)
  • release.yaml is trusted by PyPI
  • release.yaml is created etc
• RELEASE.md file (can be modelled from https://github.com/jupyterhub/jupyterhub-python-repo-template/blob/main/RELEASE.md)