add whatsnew

Author: kumaraditya303

Doc/whatsnew/3.12.rst

@@ -102,6 +102,22 @@ New Modules
 Improved Modules
 ================
 
+asyncio
+-------
+
+* On Linux, :mod:`asyncio` uses :class:`~asyncio.PidfdChildWatcher` by default
+  if :func:`os.pidfd_open` is available instead of
+  :class:`~asyncio.ThreadedChildWatcher`.
+  (Contributed by Kumar Aditya in :gh:`98024`.)
+
+* :class:`~asyncio.MultiLoopChildWatcher`, :class:`~asyncio.FastChildWatcher`
+  and :class:`~asyncio.SafeChildWatcher` child watchers are deprecated and
+  will be removed in Python 3.14. It is recommended to not manually
+  configure child watcher as the event loop now uses the best available
+  child watcher for the platform.
+  (Contributed by Kumar Aditya in :gh:`94597`.)
+
+
 pathlib
 -------