Make h2 and h3 different size in the form editor

[MAILPOET-2613]

assets/css/src/components/formEditor/components/_block_editor.scss

@@ -40,3 +40,8 @@
     width: 100%;
   }
 }
+
+// Wordpress displays h3 and h2 the same size by default. To make it less confusing we need to make h2 different size.
+h2 {
+  font-size: 1.7em;
+}