Add a license to the dataset

[pdejorge]

Hi, I have made some work building on top of the IDD dataset for segmentation (as have many other researchers previously). However, this dataset has no license so, by default, without any copyright license, releasing anything that has used the IDD data (e.g. model checkpoints, modified images with augmentations, etc) is illegal. Same goes for code repositories too.

See: https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/licensing-a-repository

Please consider adding a license to the IDD dataset so that it can be used more widely.