While this is still in discussion, we can have a look, how similar is done in Laravel framework, which is deeply loved by a lot of php devs.

The documentation:

• is divided into sections and pages. Makes it easy to find what you need, goes from basic to advanced things.
• has framework versions (divided by gh branches). Even the navigation sidebar changes from version to version and has different sections.
• is held in a separate repository. Easy to contribute, maintain and see the differences from version to version. (3000+ commits, 400+ contributors)
• has search input box. Easy to find what you need when you are already in the docs.
• has great seo. Google laravel xxx - 99% you get to the docs.

The website is also held in an open repository so that everyone can see, how it is build. It is also updated to the latest version of the framework.