Add basic datasets

[t-rutten]

We'd like to add datasets like those available through PyTorch, Tensorflow, Hugging Face, and scikit-learn. Here's a non-comprehensive list to get started:

Text

• [x] IMDB reviews
• [ ] WMT translation
• [x] Yelp reviews
• [x] SQuAD

Vision

• [x] Caltech 101
• [ ] CelebA
• [ ] ImageNet
• [x] KMNIST
• [ ] Cityscapes

Misc.

• [x] Iris
• [x] Wine recognition
• [ ] Generated datasets (see scikit-learn)