Add release note

Author: weirdwater

packages/pluggable-widgets-tools/CHANGELOG.md

@@ -6,6 +6,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased]
 
+### Changed
+
+-   We migrated to pnpm as our package manager. Users of the widgets tools should be able to continue using their package manager of choice.
+
 ## [10.21.2] - 2025-07-02
 
 ### Changed