docs: Change Discord link on README (#23378)

now it's directed to #welcome instead of #general

README.md

@@ -17,7 +17,7 @@ The aim of the project is to create an easy to use, lightweight, cross-browser,
 [Questions](https://stackoverflow.com/questions/tagged/three.js) —
 [Forum](https://discourse.threejs.org/) —
 [Slack](https://join.slack.com/t/threejs/shared_invite/zt-rnuegz5e-FQpc6YboDVW~5idlp7GfDw) —
-[Discord](https://discordapp.com/invite/HF4UdyF)
+[Discord](https://discord.gg/56GBJwAnUS)
 
 ### Usage ###