Issue #3498548: Fix documentation typos

Closes #3498548

ckeditor5_plugin_starter_template/js/ckeditor5_plugins/demoPlugin/src/simpleboxediting.js

@@ -18,7 +18,7 @@ import InsertSimpleBoxCommand from './insertsimpleboxcommand';
  *
  * Which is converted for the browser/user as this markup
  * <section class="simple-box">
- *   <h2 class="simple-box-title"></h1>
+ *   <h2 class="simple-box-title"></h2>
  *   <div class="simple-box-description"></div>
  * </section>
  *
@@ -123,7 +123,7 @@ export default class SimpleBoxEditing extends Plugin {
       },
     });
 
-    // If <h2 class="simple-box-description"> is present in the existing markup
+    // If <div class="simple-box-description"> is present in the existing markup
     // processed by CKEditor, then CKEditor recognizes and loads it as a
     // <simpleBoxDescription> model, provided it is a child element of
     // <simpleBox>, as required by the schema.