The CRD documentation is generated from the CRD manifest files, which are in turn generated from the operator source code. All the documentation strings are doc strings in the Rust source code. If you want to contribute documentation for a particular field, this needs to be done in doc string of the property on the struct that makes up that part of the CRD.

To change the UI, adjust the HTML template and CSS files in the crddocs repository. Also consult the README in that repository to learn more about how the site is generated.