Add changelog notes

Author: jasongrout

docs/source/changelog.md

@@ -44,11 +44,11 @@ If you are developing a custom widget or widget manager, here are some major cha
   - Widgets will now need correct `_model_module` and `_view_module` Unicode traits defined.
   - Selection widgets now sync the index of the selected item, rather than the label. ([#1262](https://github.com/jupyter-widgets/ipywidgets/pull/1262))
   - The Python `ipywidget.domwidget.LabeledWidget` is now `ipywidget.widget_description.DescriptionWidget`, and there is a new `ipywidget.widget_description.DescriptionStyle` that lets the user set the CSS width of the description.
-  - Custom serializers can now return a structure that contains binary objects (`memoryview`, `bytearray`, or Python 3 `bytes` object). In this case, the sync message will be a binary message, which is much more efficient for binary data than base64-encoding. ([#1194](https://github.com/jupyter-widgets/ipywidgets/pull/1194), [#1595](https://github.com/jupyter-widgets/ipywidgets/pull/1595))
+  - Custom serializers can now return a structure that contains binary objects (`memoryview`, `bytearray`, or Python 3 `bytes` object). In this case, the sync message will be a binary message, which is much more efficient for binary data than base64-encoding. The Image widget now uses this binary synchronization. ([#1194](https://github.com/jupyter-widgets/ipywidgets/pull/1194), [#1595](https://github.com/jupyter-widgets/ipywidgets/pull/1595), [#1643](https://github.com/jupyter-widgets/ipywidgets/pull/1643))
 - On the Javascript side:
   - The `jupyter-js-widgets` Javascript package has been split into `@jupyter-widgets/base` package (containing base widget classes, the DOM widget, and the associated layout and style classes), and the `@jupyter-widgets/controls` package (containing the rest of the Jupyter widgets controls). Authors of custom widgets will need to update to depend on `@jupyter-widgets/base` instead of `jupyter-js-widgets` (if you use a class from the controls package, you will also need to depend on `@jupyter-widgets/controls`). See the [cookie cutter](https://github.com/jupyter-widgets/widget-cookiecutter) to generate a simple example custom widget using the new packages.
   - Custom serializers in Javascript are now synchronous, and should return a snapshot of the widget state. The default serializer makes a copy of JSONable objects. ([#1270](https://github.com/jupyter-widgets/ipywidgets/pull/1270))
-  - Custom serializers can now return a structure that contains binary objects (`ArrayBuffer`, `DataView`, or a typed array such as `Int8Array`, `Float64Array`, etc.). In this case, the sync message will be a binary message, which is much more efficient for binary data than base64-encoding. ([#1194](https://github.com/jupyter-widgets/ipywidgets/pull/1194))
+  - Custom serializers can now return a structure that contains binary objects (`ArrayBuffer`, `DataView`, or a typed array such as `Int8Array`, `Float64Array`, etc.). In this case, the sync message will be a binary message, which is much more efficient for binary data than base64-encoding. The Image widget now uses this binary synchronization. ([#1194](https://github.com/jupyter-widgets/ipywidgets/pull/1194), [#1643](https://github.com/jupyter-widgets/ipywidgets/pull/1643))
   - A custom serializer is given the widget instance as its second argument, and a custom deserializer is given the widget manager as its second argument.
   - The Javascript model `.id` attribute has been renamed to `.model_id` to avoid conflicting with the Backbone `.id` attribute. ([#1410](https://github.com/jupyter-widgets/ipywidgets/pull/1410))
 - Regarding widget managers and the syncing message protocol: