Document codebase and generate web docs with Sphinx

[daemon]

1. Document the codebase.
2. Generate HTML documentation using Sphinx with the Napoleon and autodoc extensions.
3. Write some tutorials and getting started guides.
4. Create a GitHub page for Howl with the root directory set to docs/.

See https://flask.palletsprojects.com/en/1.1.x/ for a good Sphinx example.