Add ImageNet toy datasets from fastai
Thanks for your contribution, @mariosasko. Are you still interested in adding this dataset?

We are removing the dataset scripts from this GitHub repo and moving them to the Hugging Face Hub: https://huggingface.co/datasets

We would suggest you create this dataset there. Please, feel free to tell us if you need some help.
Adds the ImageNet toy datasets from FastAI: Imagenette, Imagewoof and Imagewang.

TODOs:
* [ ] add dummy data
* [ ] add dataset card
* [ ] generate `dataset_info.json`