Added whatsnew note for new check_order param

Author: amilbourne

doc/source/whatsnew/v1.2.0.rst

@@ -223,6 +223,7 @@ Other enhancements
 - :class:`DataFrame` now supports ``divmod`` operation (:issue:`37165`)
 - :meth:`DataFrame.to_parquet` now returns a ``bytes`` object when no ``path`` argument is passed (:issue:`37105`)
 - :class:`Rolling` now supports the ``closed`` argument for fixed windows (:issue:`34315`)
+- :meth:`testing.assert_index_equal` now has a ``check_order`` parameter that allows indexes to be checked in an order-insensitive manner (:issue:`37478`)
 
 .. _whatsnew_120.api_breaking.python: