add changelog section

Author: kof

.github/PULL_REQUEST_TEMPLATE.md

@@ -6,3 +6,7 @@
 
 - [ ] Add test that verifies the modified behavior
 - [ ] Add documentation if it changes public API
+
+## Changelog
+
+Please summarize the changes in a way that makes sense inside the changelog. Feel free to add migration tips or examples if necessary.