DOC: add PR number

Author: raybellwaves

doc/whats-new.rst

@@ -64,7 +64,7 @@ New Features
   By `Justus Magin <https://github.com/keewis>`_.
 - Added ``**kwargs`` argument to :py:meth:`open_rasterio` to access overviews (:issue:`3269`).
   By `Pushkar Kopparla <https://github.com/pkopparla>`_.
-- Added ``storage_options`` argument to :py:meth:`to_zarr` (:issue:`5601`).
+- Added ``storage_options`` argument to :py:meth:`to_zarr` (:issue:`5601`, :pull:`5615`).
   By `Ray Bell <https://github.com/raybellwaves>`_, `Zachary Blackwood <https://github.com/blackary>`_ and
   `Nathan Lis <https://github.com/wxman22>`_.
 - Histogram plots are set with a title displaying the scalar coords if any, similarly to the other plots (:issue:`5791`, :pull:`5792`).