Consider deprecating go protoc plugin in favor of `protoc-gen-twirp_ruby` gem

Hello!

We :heart: Twirp at Collective Idea. We wrote it about it using our [`protoc-gen-twirp_ruby` gem](https://github.com/collectiveidea/protoc-gen-twirp_ruby) at https://collectiveidea.com/blog/archives/2024/07/24/generating-twirp-ruby-protobuf-integration-using-ruby in hopes of making it easier for Rubyists to integrate Twirp-Ruby in their projects. It's also why we opened the discussion at #114 for additional maintainers.

Given that there hasn't been much movement on open PRs for the go module, and for various other reasons discussed in our article, we were wondering if you'd be open to deprecating the go module moving forward?

We're happy to help coordinate this change for updating documentation, cleaning up stale issues, updating the wiki, etc...

Review the proposal in this issue, discussion #114, and the linked protoc-gen-twirp_ruby gem and article. Confirm whether maintainers agree to deprecate the Go module, then identify the documentation, wiki, and stale issues that need updating; done means an agreed migration plan and completed updates.

Written by the indexing model from the issue text.