Update Discord link in README

Author: f-trycua

README.md

@@ -11,7 +11,7 @@
 
   <p align="center">
     <a href="https://cua.ai" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/badge/cua.ai-0ea5e9" alt="cua.ai"></a>
-    <a href="https://discord.gg/cua" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/badge/Discord-Join%20Server-10b981?logo=discord&logoColor=white" alt="Discord"></a>
+    <a href="https://discord.com/invite/cua-ai" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/badge/Discord-Join%20Server-10b981?logo=discord&logoColor=white" alt="Discord"></a>
     <a href="https://x.com/trycua" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/twitter/follow/trycua?style=social" alt="Twitter"></a>
     <a href="https://cua.ai/docs" target="_blank" rel="noopener noreferrer"><img src="https://img.shields.io/badge/Docs-0ea5e9.svg" alt="Documentation"></a>
     <br>