These are Sphinx docs, automatically built at https://docs.wagtail.org when the main branch is committed to GitHub. To build them locally, install Wagtail's development requirements (in the root Wagtail directory):

pip install -e .[testing,docs]

To build the documentation for browsing, from this directory run:

make html

then open _build/html/index.html in a browser.

To rebuild automatically while editing the documentation, from this directory run:

sphinx-autobuild . _build

The online MyST playground at Curvenote or the MyST-Markdown VS Code Extension are helpful tools for working with the MyST syntax.