Fixes a problem when using base for the page.

The problem is when not using / before virtual files and having a base for the page nginx can search for the file in wrong location.

index.html

         window.indexLoadedTime = window.performance.now();
         console.log("(TIME) index.html loaded:\t", indexLoadedTime);
     </script>
-    <script><!--#include virtual="config.js" --></script><!-- adapt to your needs, i.e. set hosts and bosh path -->
+    <script><!--#include virtual="/config.js" --></script><!-- adapt to your needs, i.e. set hosts and bosh path -->
     <script src="utils.js?v=1"></script>
     <!--#include virtual="connection_optimization/connection_optimization.html" -->
     <script src="connection_optimization/do_external_connect.js?v=1"></script>
-    <script><!--#include virtual="interface_config.js" --></script>
+    <script><!--#include virtual="/interface_config.js" --></script>
     <script src="libs/lib-jitsi-meet.min.js?v=139"></script>
     <script src="libs/app.bundle.min.js?v=139"></script>
     <!--#include virtual="title.html" -->