DEV: Deprecate the plugin (#663)

Author: CvX

README.md

@@ -1,5 +1,8 @@
 # Assign Plugin
 
+> [!IMPORTANT]
+> This plugin has now been bundled into Discourse core. See: https://meta.discourse.org/t/bundling-more-popular-plugins-with-discourse-core/373574
+
 Allows you to assign topics and individual posts (both private and public) to a user or group.
 
 For more information, please see: https://meta.discourse.org/t/discourse-assign/58044