Sets up setup executable rule for integrating into Bazel projects

[maxwellE]

Adds a new executable rule that can be used to set up this tool in any bazel workspace

[maxwellE]

Made a PR here for the modulemap issue swiftlang/sourcekit-lsp#2243

[rockbruno]

Looks good to me, thanks Maxwell! Just one (non-blocking) comment

[maxwellE]

@rockbruno I need approval on the new GH action for the bazel build validation

[winstondu]

@maxwellE , before merging, can you update the README as well as the BUILD + Bazelmod in the example folder to demonstrate using the setup rule?

In other words, write out the example use of the setup executable rule.

[maxwellE]

@maxwellE , before merging, can you update the README as well as the BUILD + Bazelmod in the example folder to demonstrate using the setup rule?

In other words, write out the example use of the setup executable rule.

This is done

[maxwellE]

@rockbruno Need an approval again to get the GH action to run

[rockbruno]

Thanks Maxwell!