Add onStartedWaitingForNetworkConnectivity

MobileLibrary/iOS/PsiphonTunnel/PsiphonTunnel/PsiphonTunnel.h

@@ -121,6 +121,13 @@ FOUNDATION_EXPORT const unsigned char PsiphonTunnelVersionString[];
  */
 - (void)onConnected;
 
+/*!
+ Called when the tunnel notices that the device has no network connectivity and
+ begins waiting to regain it. When connecitvity is regained, `onConnecting`
+ will be called.
+ */
+- (void)onStartedWaitingForNetworkConnectivity;
+
 /*!
  Called to indicate that tunnel-core is exiting imminently (usually do to
  a `stop()` call, but could be due to an unexpected error).