Nacos example module

This module contains some examples for nacos.

1. Run the Nacos service in standalone mode locally. By default, it uses port 8848.
2. App.java file is a simple "Hello Nacos" program.
3. ConfigExample.java file demonstrates how to utilize the configuration center in Nacos.
4. NamingExample.java file demonstrates how to use Nacos for service register, deregister, and subscribe.