change directory for turn server conf

It should be app/public/config/config.js

README.md

@@ -113,7 +113,7 @@ To integrate with an LMS (e.g. Moodle), have a look at [LTI](LTI/LTI.md).
 
 ## TURN configuration
 
-* You need an additional [TURN](https://github.com/coturn/coturn)-server for clients located behind restrictive firewalls! Add your server and credentials to `app/config.js`
+* You need an additional [TURN](https://github.com/coturn/coturn)-server for clients located behind restrictive firewalls! Add your server and credentials to `app/public/config/config.js`
 
 ## Community-driven support