Add dispose for websocket client and ping controller

Author: renefloor

packages/stream_core/lib/src/ws/client/web_socket_client.dart

@@ -81,6 +81,12 @@ class WebSocketClient implements WebSocketEngineListener, WebSocketPingClient {
 
     engine.disconnect(code.code, source.toString());
   }
+
+  void dispose() {
+    pingController.dispose();
+    _connectionStateStreamController.close();
+    _events.close();
+  }
   //#endregion
 
   //#region WebSocketEngineListener

packages/stream_core/lib/src/ws/client/web_socket_ping_controller.dart

@@ -59,6 +59,11 @@ class WebSocketPingController {
   void _cancelPongTimeoutTimer() {
     _pongTimeoutTimer?.cancel();
   }
+
+  void dispose() {
+    _pongTimeoutTimer?.cancel();
+    _pingTimer?.cancel();
+  }
 }
 
 abstract interface class WebSocketPingClient {