Support bzlmod

[alexeagle]

• Create MODULE.bazel file and e2e test in this repo
• Setup the Publish-to-BCR app and publish a release to the Bazel Central Registry
• Provide instructions for bzlmod users
• Gazelle extension should work with bzlmod

[chrismgrayftsinc]

This seems at least partially done with #170

[alexeagle]

Seems that there's not a dedicated "e2e" test module, the whole repo is used in the bcr testing. https://github.com/bazelbuild/bazel-central-registry/blob/main/modules/contrib_rules_jvm/0.13.0/presubmit.yml#L13

The Publish-to-BCR app isn't configured, but a release was done manually.

I don't think instructions were updated nor is the gazelle module accessible so I'll leave this open.

[vorburger]

https://registry.bazel.build/modules/contrib_rules_jvm ? (I have NOT tried it.)

[shs96c]

We ship everything in one unit rather than breaking out the gazelle plugin separately. Adding a bzlmod dep on contrib_rules_jvm should make everything available.