Add whatsnew entry

Author: bouweandela

docs/src/whatsnew/latest.rst

@@ -91,7 +91,8 @@ This document explains the changes made to Iris for this release
 💣 Incompatible Changes
 =======================
 
-#. N/A
+#. `@bouweandela`_ updated cube comparison so cubes with data containing a 
+   :obj:`numpy.nan` are now considered equal (:pull:`5713`)
 
 
 🚀 Performance Enhancements
@@ -113,6 +114,8 @@ This document explains the changes made to Iris for this release
 
 #. `@bouweandela`_ made comparing coordinates and arrays to themselves faster. (:pull:`5691`)
 
+#. `@bouweandela`_ made comparing cubes to themselves faster. (:pull:`5713`)
+
 
 🔥 Deprecations
 ===============