docs: enable qapidoc transmogrifier for QEMU QMP Reference

We are not enabling the transmogrifier for QSD or QGA yet because we
don't (yet) have a way to create separate indices, and all of the
definitions will bleed together, which isn't so nice.

For now, QMP is better than nothing at all!

Signed-off-by: John Snow <jsnow@redhat.com>
Message-ID: <20250311034303.75779-62-jsnow@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

docs/interop/qemu-qmp-ref.rst

@@ -7,3 +7,4 @@ QEMU QMP Reference Manual
    :depth: 3
 
 .. qapi-doc:: qapi/qapi-schema.json
+   :transmogrify:

qapi/qapi-schema.json

@@ -5,6 +5,8 @@
 #
 # This document describes all commands currently supported by QMP.
 #
+# For locating a particular item, please see the `qapi-index`.
+#
 # Most of the time their usage is exactly the same as in the user
 # Monitor, this means that any other document which also describe
 # commands (the manpage, QEMU's manual, etc) can and should be