Add AP fallback to protocol docs

docs/connection.md

@@ -6,6 +6,8 @@ An AP is randomly picked from that list to connect to.
 
 The connection is done using a bare TCP socket. Despite many APs using ports 80 and 443, neither HTTP nor TLS are used to connect.
 
+If `http://apresolve.spotify.com` is unresponsive, `ap.spotify.com:80` is used as a fallback.
+
 ## Connection Hello
 The first 3 packets exchanged are unencrypted, and have the following format :