docs: Live reload with sphinx-autobuild (#1323)

- [x] it works 🎉 
- [x] sphinx-autobuild was already included in pyproject.toml, was there
already a way to rebuild on change?
- [x] let's paint that bike shed and decide on the `tox -e <name>` for
this

tox.ini

@@ -49,6 +49,16 @@ commands_pre =
 commands =
     sphinx-build -W --keep-going docs/ docs/_build/html
 
+[testenv:docs-live]
+description = Live development: build the Sphinx docs with autoreloading enabled
+deps = {[testenv:docs]deps}
+commands_pre =
+    {[testenv:docs]commands_pre}
+# https://github.com/sphinx-doc/sphinx-autobuild/issues/170
+change_dir = {tox_root}/docs
+commands =
+    sphinx-autobuild ./ ./_build/html --watch . --port 8000
+
 [testenv:fmt]
 description = Apply coding style standards to code
 deps =