Add changelog entry for READ/WRITE fix

Author: musicinmybrain

CHANGELOG.rst

@@ -7,6 +7,11 @@ Changelog
 .. This document is user facing. Please word the changes in such a way
 .. that users understand how the changes affect the new version.
 
+version 0.5.0-dev
+-----------------
++ Fix a bug where READ and WRITE in zlib_ng.gzip_ng were inconsistent with the
+  values in gzip on Python 3.13
+
 version 0.4.3
 -----------------
 + Fix a bug where files larger than 4GB could not be decompressed.