feat: modules (broken, checkpoint)

[peakschris]

I'm attempting to add basic support for modules to this repo, so at least it can be pulled into a MODULE.bazel file directly from github in the interim whilst we are waiting for it on bcr.

This checkpoint has basic support, but I'm stumped on a particular error, and need some help to move forwards. The current error is:

> cd examples
> bazel build //...
ERROR: no such package '@@antlr3_runtime//jar': The repository '@@antlr3_runtime' could not be resolved: Repository '@@antlr3_runtime' is not defined
ERROR: D:/workdir/github/peakschris/rules_antlr/examples/antlr3/C/src/BUILD.bazel:3:6: every rule of type antlr implicitly depends upon the target '@@antlr3_runtime//jar:jar', but this target could not be found because of: no such package '@@antlr3_runtime//jar': The repository '@@antlr3_runtime' could not be resolved: Repository '@@antlr3_runtime' is not defined
Documentation for implicit attribute deps of rules of type antlr:
The dependencies to use. Defaults to the most recent ANTLR 3 release,
but if you need to use a different version, you can specify the
dependencies here.

[peakschris]

@albertocavalcante