📝 docs(async-api.mdx): add response example for async API request to improve documentation clarity

docs/docs/guidelines/async-api.mdx

@@ -27,6 +27,22 @@ curl -X POST \
   -d '{"inputs": {"text": ""}, "tweaks": {}, "sync": false}'
 ```
 
+Response:
+
+```json
+{
+  "result": {
+    "output": "..."
+  },
+  "task": {
+    "id": "...",
+    "href": "api/v1/task/<task_id>"
+  },
+  "session_id": "...",
+  "backend": "..." // celery or anyio
+}
+```
+
 ## Checking Task Status
 
 You can check the status of an asynchronous task by making a GET request to the `/task/{task_id}` endpoint.