feat: add MiniCPM 2B demo

[yirongjie]

What's New

1. Single inference support for the MiniCPM 2B model in file examples/demo_minicpm.

root@a78cffcf5fac:~/research/dev/mllm/bin# /root/research/dev/mllm/bin/demo_minicpm
[Q] <用户>Hello, who are you?<AI>
[A]  Hello! I'm an AI language model created by OpenAI, specifically designed to understand and respond to human language. My purpose is to assist you with any questions or tasks you may have, and to provide you with helpful and informative responses. I'm here to help you learn, explore, and have fun!
[Q] <用户>山东省最高的山是哪座山, 它比黄山高还是矮？差距多少？<AI>
[A]  山东省最高的山是泰山，海拔1545米。黄山位于中国安徽省，海拔1864米。因此，泰山比黄山矮，差距为319米。
[Q] <用户>Please introduce Beijing University of Posts and Telecommunications.<AI>
[A]  Beijing University of Posts and Telecommunications (BUPT) is a prestigious higher education institution in China, specializing in the fields of telecommunications, information technology, and related disciplines. Established in 1955, BUPT has a rich history and a strong reputation for academic excellence and innovation.

The university is located in Beijing, the capital city of China, and is known for its beautiful campus and modern facilities. BUPT offers a wide range of undergraduate, graduate, and postgraduate