chore: add discord button

Author: tianzhou

README.md

@@ -8,6 +8,7 @@
 
 <p align="center">
   <a href="https://cursor.com/install-mcp?name=dbhub&config=eyJjb21tYW5kIjoibnB4IEBieXRlYmFzZS9kYmh1YiIsImVudiI6eyJUUkFOU1BPUlQiOiJzdGRpbyIsIkRTTiI6InBvc3RncmVzOi8vdXNlcjpwYXNzd29yZEBsb2NhbGhvc3Q6NTQzMi9kYm5hbWU%2Fc3NsbW9kZT1kaXNhYmxlIiwiUkVBRE9OTFkiOiJ0cnVlIn19"><img src="https://cursor.com/deeplink/mcp-install-dark.svg" alt="Add dbhub MCP server to Cursor" height="32" /></a>
+  <a href="https://discord.gg/BjEkZpsJzn"><img src="https://img.shields.io/discord/1234567890?color=5865F2&logo=discord&logoColor=white&label=Discord" alt="Join our Discord" height="32" /></a>
 </p>
 
 DBHub is a universal database gateway implementing the Model Context Protocol (MCP) server interface. This gateway allows MCP-compatible clients to connect to and explore different databases.