docs: add R language implementation (#92)

Author: laresbernardo

README.md

@@ -1167,6 +1167,7 @@ Task: Return only users with role "user" as TOON. Use the same header. Set [N] t
 - **OCaml:** [ocaml-toon](https://github.com/davesnx/ocaml-toon)
 - **PHP:** [toon-php](https://github.com/HelgeSverre/toon-php)
 - **Python:** [python-toon](https://github.com/xaviviro/python-toon)
+- **R**: [toon](https://github.com/laresbernardo/toon)
 - **Ruby:** [toon-ruby](https://github.com/andrepcg/toon-ruby)
 - **Swift:** [TOONEncoder](https://github.com/mattt/TOONEncoder)