Require Ruby Gems

Repl.it now supports Ruby Gems, allowing users to easily install and use Ruby modules without having to add files. The implementation works differently from Node.js and Python implementations, using a gemspec defined in the code with bundler/inline feature. This allows for easy usage of Repl.it without requiring additional file setup. Improvements are being made, including per-repl caching and Gemfile support, and feedback is welcome.