Add border to top of add-user-note button (#39)

assets/javascripts/discourse/initializers/enable-user-notes.js.es6

@@ -90,6 +90,7 @@ export default {
             label: "user_notes.attach",
             action: "showUserNotes",
             secondaryAction: "closeAdminMenu",
+            className: "add-user-note",
           })
         );
       });

assets/stylesheets/user_notes.scss

@@ -82,3 +82,7 @@
     }
   }
 }
+
+.add-user-note {
+  border-top: 1px solid rgba(var(--primary-low-rgb), 0.5);
+}