notes.js: also return the original content when getting form data

app/assets/javascripts/notes.js

@@ -1280,10 +1280,12 @@ export default class Notes {
    * Get data from Form attributes to use for saving/submitting comment.
    */
   getFormData($form) {
+    const content = $form.find('.js-note-text').val();
     return {
       formData: $form.serialize(),
-      formContent: _.escape($form.find('.js-note-text').val()),
+      formContent: _.escape(content),
       formAction: $form.attr('action'),
+      formContentOriginal: content,
     };
   }