docs/sphinx: create QAPI domain extension stub

A Sphinx domain is a collection of directive and role extensions meant
to facilitate the documentation of a specific language. For instance,
Sphinx ships with "python" and "cpp" domains. This patch introduces a
stub for the "qapi" language domain.

Please see https://www.sphinx-doc.org/en/master/usage/domains/index.html
for more information.

This stub doesn't really do anything yet, we'll get to it brick-by-brick
in the forthcoming commits to keep the series breezy and the git history
informative.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20250311034303.75779-4-jsnow@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
diff --git a/docs/conf.py b/docs/conf.py
index 31bb9a3..49d9de8 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -60,7 +60,14 @@
 # Add any Sphinx extension module names here, as strings. They can be
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
-extensions = ['kerneldoc', 'qmp_lexer', 'hxtool', 'depfile', 'qapidoc']
+extensions = [
+    'depfile',
+    'hxtool',
+    'kerneldoc',
+    'qapi_domain',
+    'qapidoc',
+    'qmp_lexer',
+]
 
 if sphinx.version_info[:3] > (4, 0, 0):
     tags.add('sphinx4')