My name is Devin, I’m one of the software engineers on the Algolia documentation team.
For the Algolia documentation, we use a custom built static site generator named frontman. It’s written in Ruby and supports templating in ERB, HAML, and Slim.
If you’re looking for something more out-of-the-box, you can use platforms like Docusaurus (which has an Algolia plugin for DocSearch, our free documentation search solution for open source projects) or Gatsby (which has an Algolia plugin that’s in beta).
Please note that these are also static site generators, and not really CMS’s.
I hope this helps, let me know if you have any other questions.