You can use the make command and make html to build web pages.

You need a Python environment with sphinx and other dependencies, you can create it by running scripts/initenv.sh from the repository root.

To develop/change documentation, you can then do:

. venv/bin/activate
cd doc
make auto 

A page will open at https://127.0.0.1:8000/ serving the docs and it will react to changes to source files pretty fast.