Refactoring Script for Modularization

[cfeng-dev]

As our project grows in complexity, it becomes essential to improve code organization through modularization. The goal is to refactor the main script into several smaller, reusable modules to enhance code readability, maintainability, and scalability.

• Create mqttActionHandler Module: Export functions related to MQTT actions like publishing messages and checking connection status.
• Create mqttEventHandler Module: Define and export callback functions for MQTT events.
• Create mqttConnectionHandler Module: Set up the MQTT client, including initializing connections and handling connection logic.
• Create domUtils Module: Export common DOM interaction functions such as appending messages and clearing display content.
• Integration Testing: Ensure that all modules work together seamlessly and the overall functionality of the application remains intact.