Support bzlmod

[kriscfoster]

Some people who would like to use this are probably already on bzlmod. We should support that before v1.0.0.

[chickenandpork]

@kriscfoster resolved by #26 ?

[kriscfoster]

Yes good catch, forgot to close this. rules_docker_compose is in BCR now - https://registry.bazel.build/modules/rules_docker_compose_test