replace gitter chat with discord.

Author: appleboy

README.md

@@ -1,6 +1,6 @@
 # Gitea: Homebrew
 
-[![Join the chat at https://gitter.im/go-gitea/gitea](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/go-gitea/gitea?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Join the chat at https://img.shields.io/discord/322538954119184384.svg](https://img.shields.io/discord/322538954119184384.svg)](https://discord.gg/NsatcWJ)
 
 Homebrew repository to install Gitea on macOS.