If you would like to add a new category, please create an issue and then we will talk about this new category. So far, we have some categories and what we would like is to create more content on those categories and not create new categories with just 1 or 2 links/interesting thing inside.
Your PR adds some new categories and it's not well-organised, with this, it's hard to review the entire PR.
We're not using .rb files, look at the others sections.
Also, this repo is meant to be primarily a discussion, not a lot of ruby files without commentary.
best-ruby/idiomatic_ruby/collect_vs_select.md see the diff commits.