Connection quality (#27)

* update protos

* signal event

* implemented

* format

* implement example

* protocol 5

* icon size

lib/src/types.dart

@@ -8,6 +8,7 @@ enum ProtocolVersion {
   protocol2,
   protocol3,
   protocol4,
+  protocol5,
 }
 
 enum ConnectionState {
@@ -16,6 +17,13 @@ enum ConnectionState {
   reconnecting,
 }
 
+enum ConnectionQuality {
+  unknown,
+  poor,
+  good,
+  excellent,
+}
+
 enum Reliability {
   reliable,
   lossy,