Bring in zed-sorbet? (another language server)

[andyw8]

I discovered zed-sorbet by @notchairmk and it seems to be working well. I think it would be good to bring this into the Ruby extension so it's available 'out of the box'.

The implementation is only ~160 lines. There's one open issue that may need addressed first.

[notchairmk]

I had initially proposed this in #9 before making the separate extension, so either way works for me.