Added whatsnew entry

Author: Mateusz Górski

doc/source/whatsnew/v1.0.0.rst

@@ -451,6 +451,7 @@ Reshaping
 - Fix to ensure all int dtypes can be used in :func:`merge_asof` when using a tolerance value. Previously every non-int64 type would raise an erroneous ``MergeError`` (:issue:`28870`).
 - Better error message in :func:`get_dummies` when `columns` isn't a list-like value (:issue:`28383`)
 - Bug :meth:`Series.pct_change` where supplying an anchored frequency would throw a ValueError (:issue:`28664`)
+- Bug where :meth:`DataFrame.equals` returned True incorrectly in some circumstances(:issue:`28839`)
 
 Sparse
 ^^^^^^