Add release note for #12639 to 6.5 release page

docs/releases/6.5.md

@@ -13,6 +13,7 @@ depth: 1
 
 ### Other features
 
+ * Add `WAGTAIL_` prefix to Wagtail-specific tag settings (Aayushman Singh)
  * Implement `normalize` on `TypedTableBlock` to assist with setting `default` and `preview_value` (Sage Abdullah)
 
 ### Bug fixes