Add link to stable firefox version.

site/index.html

@@ -64,6 +64,7 @@
 		  Download the Safe Links Cleaner beta version for
 		  Mozilla Firefox Browser.
 		</p>
+                <a class="btn btn-pink" href="https://addons.mozilla.org/en-US/firefox/addon/safe-links-cleaner/">Stable</a>
                 <a class="btn btn-pink" href="safelinks-cleaner-firefox-beta.xpi">Beta</a>
               </div><!--//item-inner-->
             </div><!--//item-->