3.13 What's New: Add PEP 702 (python#118922)

I honestly forgot this slipped into 3.13, but I think it's worth highlighting more, as it is a PEP-sized change that makes the type system significantly more powerful.

@Yhg1s I think it's also worth mentioning in your release announcements.

Doc/whatsnew/3.13.rst

@@ -104,6 +104,9 @@ New typing features:
 * :pep:`696`: Type parameters (:data:`typing.TypeVar`, :data:`typing.ParamSpec`,
   and :data:`typing.TypeVarTuple`) now support defaults.
 
+* :pep:`702`: Support for marking deprecations in the type system using the
+  new :func:`warnings.deprecated` decorator.
+
 * :pep:`742`: :data:`typing.TypeIs` was added, providing more intuitive
   type narrowing behavior.