Add docs about sphinx-autobuild (#13011)

Co-authored-by: Adam Turner <[email protected]>

Author: jdillard

doc/internals/contributing.rst

@@ -270,12 +270,14 @@ you to preview in :file:`build/sphinx/html`.
 
 You can also build a **live version of the documentation** that you can preview
 in the browser. It will detect changes and reload the page any time you make
-edits. To do so, run the following command:
+edits.
+To do so, use `sphinx-autobuild`_ to run the following command:
 
 .. code-block:: shell
 
    sphinx-autobuild ./doc ./build/sphinx/
 
+.. _sphinx-autobuild: https://github.com/sphinx-doc/sphinx-autobuild
 
 Translations
 ~~~~~~~~~~~~

doc/usage/quickstart.rst

@@ -148,6 +148,17 @@ Sphinx will build HTML files.
    Refer to the :doc:`sphinx-build man page </man/sphinx-build>`
    for all options that :program:`sphinx-build` supports.
 
+You can also build a **live version of the documentation** that you can preview
+in the browser.
+It will detect changes and reload the page any time you make edits.
+To do so, use `sphinx-autobuild`_ to run the following command:
+
+.. code-block:: console
+
+   $ sphinx-autobuild source-dir output-dir
+
+.. _sphinx-autobuild: https://github.com/sphinx-doc/sphinx-autobuild
+
 However, :program:`sphinx-quickstart` script creates a :file:`Makefile` and a
 :file:`make.bat` which make life even easier for you. These can be executed by
 running :command:`make` with the name of the builder. For example.