Link the documentation.

Resources/views/Collector/mysqlnd.html.twig

@@ -34,6 +34,7 @@
    <tr><td>{{ key }}</td><td>{{ value }}</td></tr>
     {% endfor %}
     </table>
+    <p>Documentation on the individual statistics can be found on <a href="http://php.net/mysqlnd.stats">http://php.net/mysqlnd.stats</a>.</p>
     {% else %}
     <strong>No statistics collected for this request.</strong>
     <p>For collecting data PHP requires the mysqli extension and must use mysqlnd as Client API Library.</p>