fix web attachments and ws

packages/stream_chat/lib/src/ws/websocket.dart

@@ -121,7 +121,8 @@ class WebSocket with TimerHelper {
     _logger?.info('Closing connection with $baseUrl');
     if (_webSocketChannel != null) {
       _unsubscribeFromWebSocketChannel();
-      _webSocketChannel?.sink.close(status.goingAway);
+      _webSocketChannel?.sink
+          .close(_manuallyClosed ? status.normalClosure : status.goingAway);
       _webSocketChannel = null;
     }
   }

packages/stream_chat_flutter/lib/src/extension.dart

@@ -1,6 +1,7 @@
 import 'package:characters/characters.dart';
 import 'package:diacritic/diacritic.dart';
 import 'package:file_picker/file_picker.dart';
+import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:stream_chat_flutter/src/emoji/emoji.dart';
 import 'package:stream_chat_flutter/src/localization/translations.dart';