Update CHANGELOG.md with image widget placeholder fix

Adds changelog entry documenting the fix for image widgets failing to display placeholders when selected images are archived, resulting in empty _image relationships.

Author: skosarin

packages/apostrophe/CHANGELOG.md

@@ -7,6 +7,7 @@
 
 ### Fixes
 
+* Fixes an issue where an image widget could fail to display its placeholder after the selected image is archived, leaving an empty `_image` relationship.
 * Fixes an issue where the frontend was caching stale choices for `select`, `radio` and `checkboxes` fields that were saved but no longer valid (i.e removed from the schema).
 * When we reach the max in a widget area, the `Add Content` button is now disabled.