Brush up RBS and related tools for practical Rails apps

RBS, a type annotation language and tool for Ruby, is about to be bundled with Ruby 3.0. Gradual typing with RBS allows Rubyists to enjoy the benefits of static analysis.

However, RBS is still a developing technology and its immediate applicability is somewhat unknown. In particular, it is an important task to verify and improve the practicality of RBS in Rails apps, where Ruby is typically used.

I'll apply RBS and its related software to real Rails apps and examine their utility. Steep, a static analysis tool that uses RBS, and RBS Rails, a tool that facilitates the use of RBS in Rails apps, will be targeted for the investigation. I aim to complement the implementation and improve its completeness until they reach a practical level.