Hi, this pull request adds support for RBS files for the Ruby language.
[RBS](https://github.com/ruby/rbs) is a language to describe the
structure of Ruby programs.
This pull request:
- adds a new grammar to the Ruby extension for RBS
https://github.com/joker1007/tree-sitter-rbs
- configures the Ruby extension to use the added grammar.
Release Notes:
- N/A
