Add official Ruby sdk

I'm super thrilled about Iggy! 🎉

Just wanted to add an issue that could be used to track a Ruby SDK/client.

I also wanted to mention two rust<>ruby projects that might be useful for implementing a Ruby SDK.

https://github.com/matsadler/magnus
https://github.com/danielpclark/rutie

With either of these, I think it should be possible to basically wrap the existing Rust client with a Ruby layer.

I don't know rust, but would be happy to provide some feedback on the API surface for a potential Ruby client if that's useful (I think following the Iggy Node client structure would be a very good starting point).

Start by reviewing the existing Rust client and the Iggy Node client structure to understand the intended SDK surface. Compare Magnus and Rutie as possible Rust-to-Ruby integration approaches, then define the Ruby client's scope and API compatibility; done means an agreed, usable Ruby SDK is implemented and documented.

Written by the indexing model from the issue text.