add to whats new

Author: dnowacki-usgs

doc/whats-new.rst

@@ -21,7 +21,9 @@ v0.16.1 (unreleased)
 
 Breaking changes
 ~~~~~~~~~~~~~~~~
-
+- :py:meth:`DataArray.astype` and :py:meth:`Dataset.astype` now preserve attributes. Keep the
+  old behavior by passing `keep_attrs=False` (:issue:`2049`, :pull:`4314`).
+  By `Dan Nowacki <https://github.com/dnowacki-usgs>`_ and `Gabriel Joel Mitchell <https://github.com/gajomi>`_.
 
 New Features
 ~~~~~~~~~~~~