chat: update discord invite link

Author: avivace

website/chat.md

@@ -13,7 +13,7 @@ head:
 
 Join our community on the following channels. Before posting, read the rules and the FAQ (usually in the welcome threads or in the signup).
 
-- Discord Server: [https://discord.io/gbdev](https://discord.io/gbdev).
+- [Discord Server](https://discord.gg/RjJKA8wrD4).
 - IRC: [`#gbdev` on Libera.chat](https://web.libera.chat/#gbdev). 
   - `#gbdev-ot`, `#gbdev-hw`,`#gbdev-meta`, `#gbdev-asm`,`#gbdev-gfx`, `#gbdev-emudev` and `#gbdev-research` are also available.
 - Forum: [https://gbdev.gg8.se/forums](https://gbdev.gg8.se/forums/)