Add Slack Badge (#1668)

Add Slack badge to README

Author: drguthals

README.md

@@ -1,7 +1,7 @@
 <a name="readme-top"></a>
 # Indexify 
 
-[![Discord](https://dcbadge.vercel.app/api/server/VXkY7zVmTD?style=flat&compact=true)](https://discord.gg/VXkY7zVmTD)
+[![Slack](https://img.shields.io/badge/slack-TensorlakeCloud-purple?logo=slack)](https://join.slack.com/t/tensorlakecloud/shared_invite/zt-32fq4nmib-gO0OM5RIar3zLOBm~ZGqKg)
 
 Indexify simplifies building and serving durable, multi-stage data-intensive workflows and exposes them as HTTP APIs or Python Remote APIs.