DOC: Add a release note for the new nan<x>parameters

doc/release/upcoming_changes/20027.improvement.rst

@@ -0,0 +1,17 @@
+Missing parameters have been added to the ``nan<x>`` functions
+--------------------------------------------------------------
+A number of the ``nan<x>`` functions previously lacked parameters that were
+present in their ``<x>``-based counterpart, *e.g.* the ``where`` parameter was
+present in `~numpy.mean` but absent from `~numpy.nanmean`.
+
+The following parameters have now been added to the ``nan<x>`` functions:
+
+* nanmin: ``initial`` & ``where``
+* nanmax: ``initial`` & ``where``
+* nanargmin: ``keepdims`` & ``out``
+* nanargmax: ``keepdims`` & ``out``
+* nansum: ``initial`` & ``where``
+* nanprod: ``initial`` & ``where``
+* nanmean: ``where``
+* nanvar: ``where``
+* nanstd: ``where``