[3.13] gh-130711: Document PyBaseObject_Type (GH-130712) (GH-130792)

(cherry picked from commit b3c18bf)

Co-authored-by: Yuki Kobayashi <drsuaimqjgar@gmail.com>
Co-authored-by: Peter Bierma <zintensitydev@gmail.com>

Author: 3 people

Doc/c-api/structures.rst

@@ -63,6 +63,11 @@ under :ref:`reference counting <countingrefs>`.
    See documentation of :c:type:`PyVarObject` above.
 
 
+.. c:var:: PyTypeObject PyBaseObject_Type
+
+   The base class of all other objects, the same as :class:`object` in Python.
+
+
 .. c:function:: int Py_Is(PyObject *x, PyObject *y)
 
    Test if the *x* object is the *y* object, the same as ``x is y`` in Python.