docs: add discord invite link

Author: SWHL

README.md

@@ -11,6 +11,7 @@
 </div>
 <div>&nbsp;</div>
 
+<a href="https://discord.gg/uPBJHM8s"><img src="https://img.shields.io/badge/Chat-on%20discord-7289da.svg?sanitize=true" alt="Chat"></a>
 <a href="https://huggingface.co/spaces/RapidAI/RapidOCRv3" target="_blank"><img src="https://img.shields.io/badge/%F0%9F%A4%97-Hugging Face Demo-blue"></a>
 <a href="https://www.modelscope.cn/studios/RapidAI/RapidOCRv3.0.0/summary" target="_blank"><img src="https://img.shields.io/badge/魔搭-Demo-blue"></a>
 <a href="https://colab.research.google.com/github/RapidAI/RapidOCR/blob/main/assets/RapidOCRDemo.ipynb" target="_blank"><img src="https://raw.githubusercontent.com/RapidAI/RapidOCR/main/assets/colab-badge.svg" alt="Open in Colab"></a>