Add whatsnew text for warnings module changes.

Author: nascheme

Doc/whatsnew/3.14.rst

@@ -122,6 +122,18 @@ it's safe to do so. This can lead to different values returned from
 :func:`sys.getrefcount` and :c:func:`Py_REFCNT` compared to previous versions
 of Python.  See :ref:`below <whatsnew314-refcount>` for details.
 
+A new flag has been added, :data:`~sys.flags.context_aware_warnings`.  This
+flag defaults to true for the free-threaded build and false for the GIL-enabled
+build. If the flag is true then the :class:`warnings.catch_warnings` context
+manager uses a context variable for warning filters.
+
+A new flag has been added, :data:`~sys.flags.thread_inherit_context`. This
+flag defaults to true for the free-threaded build and false for the GIL-enabled
+build. If the flag is true then threads created with :class:`threading.Thread`
+start with a copy of the :class:`~contextvars.Context()` of the caller of
+:meth:`~threading.Thread.start`.
+
+
 New features
 ============
 
@@ -1028,6 +1040,18 @@ Please report any bugs or major performance regressions that you encounter!
 
 .. seealso:: :pep:`744`
 
+Concurrent safe warnings control
+--------------------------------
+
+The :class:`warnings.catch_warnings` context manager will now optionally
+use a context variable for warning filters.  This is enabled by setting
+the :data:`~sys.flags.context_aware_warnings` flag, either with the ``-X``
+command-line option or an environment variable.  This gives predicable
+warnings control when using :class:`~warnings.catch_warnings` combined with
+multiple threads or asynchronous tasks. The flag defaults to true for the
+free-threaded build and false for the GIL-enabled build.
+
+(Contributed by Neil Schemenauer and Kumar Aditya in :gh:`130010`.)
 
 Other language changes
 ======================