Support referencing of @v1

[consideRatio]

We have two action github repositories in the JupyterHub org where we have ended up using another GitHub action to automatically update a vX (v1, v2 etc) branch whenever we create a GitHub Release.

At this point, perhaps it would make sense to cut a 1.0.0 release which would allow users to reference @v1 and give this repo some flexibility of managing breaking and non-breaking changes.

I'd warmly recommend:

• Having a workflow like this in repo's containing a GitHub action: https://github.com/jupyterhub/action-k8s-namespace-report/blob/main/.github/workflows/release-updates.yaml
• Graduating GitHub actions to v1.0.0 quite quickly

What do you think about this @jacobtomlinson?

[jacobtomlinson]

Sounds sensible thanks!