Add DataToML to readme

Author: rom1504

Diff for: README.md

@@ -22,6 +22,8 @@ Also see [laion5B](https://laion.ai/laion-5b-a-new-era-of-open-large-scale-multi
 
 [<img src="https://github.com/rom1504/clip-retrieval/raw/main/doc_assets/clip-front-pic.png" alt="clip front" width="500">](https://rom1504.github.io/clip-retrieval/)
 
+If you believe in making reusable tools to make data easy to use for ML and you would like to contribute, please join the [DataToML](https://discord.gg/ep8yUUtCnp) chat.
+
 ## Who is using clip retrieval ?
 
 * [cah-prepro](https://github.com/rom1504/cah-prepro) preprocess the 400M image+text crawling at home dataset. clip-retrieval is used to compute 400M clip embeddings and the indices