Being very specific gem - that holds opinionated, yet as strict as it gets RuboCop linter configuration - Hix on Rails' Ruby styleguide is not really open to contributions from the outside world.
It is what we use to keep Hix on Rails codebase clean.
That said, we are always open for the discussion, and kindly invite you to explain to us in details why do you think some of our decissions could be better, code-maintenance wise.
We have a special article dedicated to configuring RuboCop in Ruby and Ruby on Rails projects - please, leave a comment!
That's the configuration only, though - if you find a way to improve any of the scripts around it, please do contribute!