add 1.3.4 whatsnew

Author: AlexeyGy

doc/source/whatsnew/v1.3.4.rst

@@ -0,0 +1,51 @@
+.. _whatsnew_134:
+
+What's new in 1.3.4 (September ??, 2021)
+----------------------------------------
+
+These are the changes in pandas 1.3.4. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_134.regressions:
+
+Fixed regressions
+~~~~~~~~~~~~~~~~~
+- :meth:`.GroupBy.mean` now supports ``NaT`` values (:issue:`43132`)
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_134.performance:
+
+Performance improvements
+~~~~~~~~~~~~~~~~~~~~~~~~
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_134.bug_fixes:
+
+Bug fixes
+~~~~~~~~~
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_134.other:
+
+Other
+~~~~~
+-
+-
+
+.. ---------------------------------------------------------------------------
+
+.. _whatsnew_134.contributors:
+
+Contributors
+~~~~~~~~~~~~
+
+.. contributors:: v1.3.3..v1.3.4|HEAD