Make viewers counter period configurable

web/template/viewer.html

@@ -50,5 +50,10 @@
     {{end}}
   ]
   startPeerConnection()
+
+  // Wait a bit before pulling viewers counter for the first time
+  setTimeout(() => {
+      refreshViewersCounter({{.Cfg.ViewersCounterRefreshPeriod}})
+  }, 1000)
 </script>
 {{end}}