Add chrome-firephp sample extensions; add sample references to devtools pages

chrome/common/extensions/docs/static/experimental.devtools.audits.html

 <!-- BEGIN AUTHORED CONTENT -->
 <p id="classSummary">
 Use the <code>chrome.experimental.devtools.audits</code> module to add new audit
 categories and rules to Developer Tools' Audit panel.
 </p><p>
 See <a href="experimental.devtools.html">DevTools APIs summary</a> for
 general introduction to using Developer Tools APIs</a>.
 </p>
 
 <h2>Notes</h2>
@@ skipping 44 matching lines @@
                     "Text should stand out from background",
                     results.Severity.Info);
 });
 </pre>
 <p>The audit result tree produced by the snippet above will look like this:
 </p>
 <img src="images/devtools-audits-results.png"
      style="margin-left: 20px"
      width="330" height="169"
      alt="Audit results example" />
+
+<h2 id="examples">Examples</h2>
+
+<p>
+You can find examples that use this API in
+<a href="samples.html#devtools.audits">Samples</a>.
+</p>
 <!-- END AUTHORED CONTENT -->