[3.14] gh-141004: Document PyMemoryView_Type (GH-141034) (GH-141054)

gh-141004: Document `PyMemoryView_Type` (GH-141034)
(cherry picked from commit 3f6aca1)

Co-authored-by: Peter Bierma <[email protected]>

Author: miss-islington

Doc/c-api/memoryview.rst

@@ -13,6 +13,12 @@ A :class:`memoryview` object exposes the C level :ref:`buffer interface
 any other object.
 
 
+.. c:var:: PyTypeObject PyMemoryView_Type
+
+   This instance of :c:type:`PyTypeObject` represents the Python memoryview
+   type. This is the same object as :class:`memoryview` in the Python layer.
+
+
 .. c:function:: PyObject *PyMemoryView_FromObject(PyObject *obj)
 
    Create a memoryview object from an object that provides the buffer interface.