v1.1.1: fix(#10) ping syntax for websockets

package.json

@@ -1,6 +1,6 @@
 {
   "name": "bitget-api",
-  "version": "1.1.0",
+  "version": "1.1.1",
   "description": "Node.js connector for Bitget REST APIs and WebSockets, with TypeScript & end-to-end tests.",
   "main": "lib/index.js",
   "types": "lib/index.d.ts",

src/websocket-client.ts

@@ -331,7 +331,7 @@ export class WebsocketClient extends EventEmitter {
     this.clearPongTimer(wsKey);
 
     this.logger.silly('Sending ping', { ...LOGGER_CATEGORY, wsKey });
-    this.tryWsSend(wsKey, JSON.stringify({ op: 'ping' }));
+    this.tryWsSend(wsKey, 'ping');
 
     this.wsStore.get(wsKey, true).activePongTimer = setTimeout(() => {
       this.logger.info('Pong timeout - closing socket to reconnect', {