chore: Update README.md (#1833)

Author: maninhill

README.md

@@ -1,5 +1,6 @@
 <p align="center"><img src= "https://github.com/1Panel-dev/maxkb/assets/52996290/c0694996-0eed-40d8-b369-322bf2a380bf" alt="MaxKB" width="300" /></p>
 <h3 align="center">基于大模型和 RAG 的知识库问答系统</h3>
+<h4 align="center">Ready-to-use, flexible RAG Chatbot</h4>
 <p align="center">
     <a href="https://trendshift.io/repositories/9113" target="_blank"><img src="https://trendshift.io/api/badge/repositories/9113" alt="1Panel-dev%2FMaxKB | Trendshift" style="width: 250px; height: auto;" /></a>
     <a href="https://market.aliyun.com/products/53690006/cmjj00067609.html?userCode=kmemb8jp" target="_blank"><img src="https://img.alicdn.com/imgextra/i2/O1CN01H5JIwY1rZ0OobDjnJ_!!6000000005644-2-tps-1000-216.png" alt="1Panel-dev%2FMaxKB | Aliyun" style="width: 250px; height: auto;" /></a>