The sphinxdocs project allows using Bazel to run Sphinx to generate
documentation. It comes with:
Rules for running Sphinx
Rules for generating documentation for Starlark code.
A Sphinx plugin for documenting Starlark and Bazel objects.
Rules for readthedocs build integration.
While it is primarily oriented towards docgen for Starlark code, the core of it is agnostic as to what is being documented.