Update CHANGELOG.md

Author: jdvanwijk

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [13.7.2]
+
+### Changed
+
+- Tree's ASCII_GUIDES and TREE_GUIDES constants promoted to class attributes
+
 ## [13.7.1] - 2024-02-28
 
 ### Fixed