adjust example html.

Author: yama-dev

examples/index.html

@@ -152,6 +152,9 @@ <h3>Custom Player</h3>
           <p class="display_time_down">00:00</p>
         </div>
 
+        <button class="btn btn btn-secondary" onclick="PMB.SeekTo(30)">Media再生位置変更(SeekTo 30s)</button>
+        <button class="btn btn btn-secondary" onclick="PMB.SeekTo(60)">Media再生位置変更(SeekTo 60s)</button>
+
         <pre class="prettyprint lang-html mt-2">
           <code>
           &lt;script&gt;
@@ -183,7 +186,9 @@ <h3>Custom Player</h3>
             Media変更 id=4231692338001&lt;br&gt;&lt;br&gt;
             &lt;p class=&quot;display_time&quot;&gt;00:00&lt;/p&gt;
             &lt;p class=&quot;display_time_down&quot;&gt;00:00&lt;/p&gt;
-          &lt;/div&gt;</code>
+          &lt;/div&gt;
+          &lt;button class=&quot;btn btn btn-secondary&quot; onclick=&quot;PMB.SeekTo(30)&quot;&gt;Media再生位置変更(SeekTo 30s)&lt;/button&gt;</code>
+          &lt;button class=&quot;btn btn btn-secondary&quot; onclick=&quot;PMB.SeekTo(60)&quot;&gt;Media再生位置変更(SeekTo 60s)&lt;/button&gt;</code>
         </pre>
       </div>