[skip-ci] add whats-new

Author: dcherian

doc/whats-new.rst

@@ -80,6 +80,8 @@ Bug fixes
 - Expand user directory paths (e.g. ``~/``) in :py:func:`open_mfdataset` and
   :py:meth:`Dataset.to_zarr` (:issue:`4783`, :pull:`4795`).
   By `Julien Seguinot <https://github.com/juseg>`_.
+- Convert to IndexVariable or Variable during renaming as appropriate. (:issue:`4107`, :issue:`4417`, :pull:`4108`)
+  By `Deepak Cherian <https://github.com/dcherian>`_.
 
 Documentation
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