Add CHANGELOG entry for the on_query_change count

Author: sevenseacat

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Features
 
 * Added `initial_load={:sync}`, which puts the first page of data in the server-rendered HTML. Thanks @Alt-iOS! ([#203](https://github.com/sevenseacat/cinder/pull/203))
+* `on_query_change` payloads now carry a `count` key with the total matching records, so parents no longer need their own `Ash.count!`. Thanks @mbaertschi! ([#208](https://github.com/sevenseacat/cinder/pull/208))
 
 ## v0.17.0 (2026-08-08)