Adopt versioning so we can experiment while not breaking user's release process

[rtyley]

Once we get more repos using gha-scala-library-release-workflow, we'll need a way to experiment and not break user's release process when, for instance, the required sbt release steps change.

• https://devopsjournal.io/blog/2022/10/19/How-GitHub-Actions-versioning-works
• https://github.com/actions/toolkit/blob/main/docs/action-versioning.md

See also:

• https://blog.gruntwork.io/introducing-git-xargs-an-open-source-tool-to-update-multiple-github-repos-753f9f3675ec