add documentation

src/config.rs

@@ -123,6 +123,9 @@ pub enum Config {
     /// because we do not want to send a second warning)
     NotifyAboutWrongPw,
 
+    /// webrtc signaling server (https://github.com/cracker0dks/basicwebrtc) that should be used for calls
+    /// Format: https://example.com/subdir?token=TOKEN
+    /// The other properties that are needed for a call such as the roomname will be set in the anchor part of the url.
     BasicWebRTCInstance,
 }