Secure domain + Coturn - Need adapted instructions (#497)

* Add hint for usage with coturn...

* Update README.md

* Update README.md

Author: Commifreak

README.md

@@ -102,6 +102,17 @@ from anonymous domain. Here's what has to be configured:
  ```
 (Note that guest.jitsi-meet.example.com is internal to jitsi, and you do not need to (and should not) create a DNS record for it, or generate an SSL/TLS certificate, or do any web server configuration.)
 
+**NOTE:** Make sure you enable desired modules to the guest virtual host like `turncredentials` (if you use STUN/TURN together with secure domain) and/or `conference_duration` etc., by adding the `modules_enabled` option:
+
+```
+VirtualHost "guest.jitsi-meet.example.com"
+    authentication = "anonymous"
+    modules_enabled = {
+     "turncredentials";
+    }
+    c2s_require_encryption = false
+```
+
 2 In Jitsi Meet config.js configure 'anonymousdomain':<br/>
 
 (If you have installed jitsi-meet from the Debian package, these changes should be made in /etc/jitsi/meet/[your-hostname]-config.js)