Add changelog

Author: mathbunnyru

CHANGELOG.md

@@ -3,6 +3,12 @@
 This changelog only contains breaking and/or significant changes manually introduced to this repository (using Pull Requests).
 All image manifests can be found in [the wiki](https://github.com/jupyter/docker-stacks/wiki).
 
+## UNRELEASED
+
+Affected: all images.
+
+- **Breaking:** `docker-stacks-foundation`: switch to Python 3.13 ([#2163](https://github.com/jupyter/docker-stacks/pull/2163)).
+
 ## 2024-11-08
 
 Affected: all images except `docker-stacks-foundation`.