MC-3775: Button editable state is not consistent with the options panel appearing

- Elaborate on decision behind focus out logic

Author: davemacaulay

app/code/Magento/PageBuilder/view/adminhtml/web/js/content-type/button-item/preview.js

@@ -46,7 +46,9 @@ export default class Preview extends BasePreview {
     }
 
     /**
-     * On focus out
+     * Handle on focus out events, when the button item is focused out we need to set our focusedButton record on the
+     * buttons preview item to null. If we detect this focus out event is to focus into another button we need to ensure
+     * we update the record appropriately.
      *
      * @param {number} index
      * @param {Event} event