feat: Whitelist option to hide lobby button.

react/features/base/config/configWhitelist.js

@@ -118,6 +118,7 @@ export default [
     'gatherStats',
     'googleApiApplicationClientID',
     'hiddenDomain',
+    'hideLobbyButton',
     'hosts',
     'iAmRecorder',
     'iAmSipGateway',