If some informations are not clear or are missing, you can fork the repository which contains the documentation, add/change something and send your pull request.
Clone with your IDE or git this repository and add the projet in your IDE.
The content of this website "docs/developer", is in the folder "docs" with his own "assets/resources". The configuration is in the root file "_config.yml".
More informations are explained by GitHub on this page https://help.github.com/articles/using-jekyll-with-pages