add index
<img width="1133" alt="Capture d’écran 2023-11-09 à 10 21 20" src="https://github.com/huggingface/datasets-server/assets/1676121/14ac4d4d-62e6-459f-b78b-92260a53415e">

add index: <img width="1133" alt="Capture d’écran 2023-11-09 à 10 21 20" src="https://github.com/huggingface/datasets-server/assets/1676121/14ac4d4d-62e6-459f-b78b-92260a53415e">
