[Feature request] Provide Python MQTT Example Codes In Documentation

### Search before asking

- [X] I searched in the [issues](https://github.com/apache/iotdb/issues) and found nothing similar.

### Motivation

Hi all,

I would to request **Python MQTT Example Codes** to be added in **MQTT Protocol documentation page** (Link: https://iotdb.apache.org/UserGuide/Master/API/Programming-MQTT.html).

The reason being is my end successfully publish data into IoTDB successfully without any errors prompted.

However, no data is stored when execute SELECT query in IoTDB CLI.

Hence, by providing working Python MQTT Example Code, it would help future developers to troubleshoot this issue.

Thanks.

### Solution

- Provide **Python MQTT Example Codes** in **Apache IoTDB MQTT Protocol documentation page** (Link: https://iotdb.apache.org/UserGuide/Master/API/Programming-MQTT.html).

### Alternatives

_No response_

### Are you willing to submit a PR?

- [X] I'm willing to submit a PR!

Start with the MQTT Protocol documentation page at https://iotdb.apache.org/UserGuide/Master/API/Programming-MQTT.html and review its existing examples and publishing guidance. Add a working Python MQTT example that helps users verify data insertion, then confirm the documentation clearly shows how to publish data and query the resulting records.

Written by the indexing model from the issue text.