add comment

src/g-icon.html

@@ -7,6 +7,7 @@ license that can be found in the LICENSE file.
   <link rel="components" href="g-component.html">
   <link rel="stylesheet" href="css/g-icon.css">
   <template>
+    <!-- nodes with id automatically appear in this.$ hash -->
     <div id="icon" class="icon" onclick="x('colorize')"></div>
   </template>
   <script>