add additional qs and header to http client; add additional queryParams to websocket

packages/stream_chat/lib/version.dart

@@ -1,6 +1,12 @@
 import 'package:stream_chat/src/client/client.dart';
+import 'package:stream_chat/src/core/platform_detector/platform_detector.dart';
 
 /// Current package version
 /// Used in [StreamChatClient] to build the `x-stream-client` header
 // ignore: constant_identifier_names
 const PACKAGE_VERSION = '2.0.0';
+
+/// Get the current user agent
+String get userAgent => 'stream-chat-dart-client-'
+    '${CurrentPlatform.name}-'
+    '${PACKAGE_VERSION.split('+')[0]}';