changelog for non-string flaglist extras

Author: alexcjohnson

CHANGELOG.md

@@ -2,6 +2,12 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## [UNRELEASED]
+
+### Updated
+
+  - Allow non-string extras in `flaglist` attributes, to support upcoming changes to `ax.automargin` in plotly.js [plotly.js#6193](https://github.com/plotly/plotly.js/pull/6193), [#3749](https://github.com/plotly/plotly.py/pull/3749)
+
 ## [5.8.0] - 2022-05-09
 
 ### Fixed