Publish Action as immutable OCI Artifact

[jontze]

Is your feature request related to a problem? Please describe.
The Action is currently published and versioned via git tags. Git tags are mutable and can never ensure that they always point to the same artifacts.

Describe the solution you'd like
Ideally the action artifacts should be published in an immutable way. It looks like GitHub is getting closer to such a feature and is offering a way to publish action artifacts as immutable OCI container: https://github.com/actions/publish-immutable-action

The action is still in public beta. When adoption grows and it's stable to use, I should consider to change the release process.