added touch advisement

examples/slider/slider-thermostat.html

@@ -25,6 +25,9 @@
   </nav>
   <main>
     <h1>Slider Examples with aria-orientation and aria-valuetext</h1>
+    <div class="advisement">
+      <p><strong>WARNING!</strong> Users of touch-based assistive technologies may not be able to fully operate widgets that implement the <code>slider</code> pattern because APIs for capturing the necessary gestures and commands from assistive technologies are not yet available. Authors should fully test <code>slider</code> widgets using assistive technologies on primarily touch devices before considering incorporation into production systems.</p>
+    </div>
     <p>
       The following example of a hypothetical online thermostat demonstrates the
       <a href="../../#slider">slider design pattern.</a>