A GitHub Action in Homebrew/brew is run on each commit, which deploys the site to GitHub Pages.
Open https://rubydoc.brew.sh in your web browser.
To instead run Homebrew RubyDoc locally, run:
git clone https://github.com/Homebrew/rubydoc.brew.sh cd rubydoc.brew.sh bundle install bundle exec jekyll serve
Code is under the BSD 2-clause "Simplified" License.