Support for legal NLP datasets (EURLEX, ECtHR cases and EU-REG-IR)
> Awesome thank you :)
> This is really cool
> 
> I left a few comments.
> 
> Also it looks like the dummy data are quite big (100-200KB each). Can you try to reduce their sizes please ? For example I noticed that all the jsonl files inside the `dummy_data.zip` files have 20 lines. Can you only keep 2 lines instead ?

Hi @lhoestq, I did my best to improve the README files, while I also decreased dummy data examples. I included one more legal dataset. @lhoestq thanks for your review.

 I shortened the examples in README files and removed `DEFAULT_CONFIG_BUILDER` from `eu_regulatory_ir.py`.
Add support for two legal NLP datasets:

- EURLEX (https://www.aclweb.org/anthology/P19-1636/)
- ECtHR cases (https://arxiv.org/abs/2103.13084)
- EU-REG-IR (https://arxiv.org/abs/2101.10726)