fix: add note about imagebuffer chanegs

Author: Julusian

for-developers/module-development/api-changes/v2.0.md

@@ -563,6 +563,12 @@ Now, `callback` is invoked whenever the feedback should run and is the only meth
 
 To help track state, `previousOptions` is now provided to the `callback`. This contains the values from the previous call so you can detect relevant changes without tracking state yourself.
 
+### Feedback `imageBuffer` format change
+
+For any advanced feedbacks producing an `imageBuffer`, we now require these to be base64 encoded strings.
+
+You can convert your existing buffer with `.toString('base64')`.
+
 ### Learn callback return value changes
 
 If you implement a `learn` callback in your actions or feedbacks, expectations for its return value have changed.