[doc] more fixes of warnings/errors in doc build
- move 3.21.rst changelog description at it's proper place
- include changelogs in the main index
- few typos
- add :noindex: for autoxxx directives not in api/
Related to #4832808
.. _appobject_module:
:mod:`cubicweb.appobject`
=========================
.. automodule:: cubicweb.appobject
.. _appobject:
.. autoclass:: AppObject
:show-inheritance:
:members: