Set up the "Publish to BCR" GitHub app

[seh]

Mirror releases of this Bazel ruleset to the Bazel Central Registry using the "Publish to BCR" GitHub app, avoiding the need to submit PRs against the bazelbuild/bazel-central-registry repository manually.

See bazelbuild/bazel-central-registry#355 for the basis from which I generalized the template files proposed here.

[Mitsuwa]

im uncertain if there is any kind of process necessary to go through with publishing private repos to the public bcr but this repo isnt really a security risk so I dont see any reason not to do this

[seh]

im uncertain if there is any kind of process necessary to go through with publishing private repos to the public bcr

Note that this GitHub repository is public.