Set up "push tag to release" workflow

[fmeum]

Adopts the release workflow from https://github.com/bazel-contrib/rules-template, which includes automatic publishing to the Bazel Central Registry (BCR).

[fmeum]

@eed3si9n Please take a look at the CONTRIBUTING.md file, releasing will require you to add the Publish to BCR app to this repo and your fork of the bazel-central-registry repo as one-time setup.

The README currently lists the first version as 0.1.0, but feel free to use a different one. Since I can't test the workflow, please let me know if anything doesn't work and I can help.

[eed3si9n]

https://github.com/bazel-contrib/publish-to-bcr/tree/main/templates#optional-configyml

fixedReleaser: GitHub username and email to use as the author for BCR commits. Set this if you want a single user to always be the author of BCR entries regardless of who cut the release.

Not sure if we want this. I guess I can always remove it, but something to note.

[eed3si9n]

Looks like it worked! - bazelbuild/bazel-central-registry#1170