docs(collection): add changelog for quickSort pdqsort enhancement

This addresses the failing 'Changelog Entry' CI check by adding the
required entry for the quickSort implementation replacement.

Author: abbashosseinii

pkgs/collection/CHANGELOG.md

@@ -9,6 +9,8 @@
 - Add `PriorityQueue.of` constructor and optimize adding many elements.
 - Address diagnostics from `strict_top_level_inference`.
 - Run `dart format` with the new style.
+- Replace `quickSort` implementation with a more performant and robust
+  Pattern-defeating Quicksort (pdqsort) algorithm.
 
 ## 1.19.1