Add a link to the /mobile page below the loading progress bar for old/limited browsers

resources/content-server/index.html

@@ -14,6 +14,7 @@
             <progress>
             </progress>
             <div>Loading, please wait&hellip;</div>
+            <div>You can also use a simple, non-javascript version of this site: <a href="mobile">here</a></div>
             <style type="text/css">
 #page_load_progress {
     position:relative;