plugin_framework, add event listening

Signed-off-by: fufesou <shuanglongchen@yeah.net>

src/client/io_loop.rs

@@ -961,6 +961,14 @@ impl<T: InvokeUiSession> Remote<T> {
                                     }
                                 });
                             }
+
+                            // on connection established client
+                            #[cfg(all(feature = "flutter", feature = "plugin_framework"))]
+                            #[cfg(not(any(target_os = "android", target_os = "ios")))]
+                            crate::plugin::handle_listen_event(
+                                crate::plugin::EVENT_ON_CONN_CLIENT,
+                                &self.handler.id,
+                            );
                         }
 
                         if self.handler.is_file_transfer() {