Add AnnotateRb

[drwl]

AnnotateRb - A Ruby Gem that adds annotations to your Rails models and route files.

I used to be a maintainer in the old gem Annotate, but made a hardfork last year and have been actively maintaining it. I would also consider removing the old gem as it's not actively maintained. The last release was over 2 years ago (v3.2.0 was released Feb 2022).

https://rubygems.org/gems/annotaterb

[drwl]

@markets let me know if there's any qualms about adding the gem. I can also submit a PR with the requested change if you want.

[markets]

Closing this one @drwl, as the main discussion is happening on #1145.