Package for Homebrew

I don't see a way to try `copybara` without compiling from source, or trying to find the right way to map docker volumes.

I am not an expert in Java, but it should be possible to package it for `brew install`.

Here are some docs for the starter.

* https://www.veracode.com/blog/secure-development/distribute-your-java-app-brew
* https://docs.brew.sh/Formula-Cookbook