Add MANtIS dataset
_The documentation is not available anymore as the PR was closed or merged._ Thanks for your contribution, @bhavitvyamalik. 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 that you create this dataset there. Please, feel free to tell us if you need some help.
This PR adds MANtIS dataset.
Arxiv: [https://arxiv.org/abs/1912.04639](https://arxiv.org/abs/1912.04639)
Github: [https://github.com/Guzpenha/MANtIS](https://github.com/Guzpenha/MANtIS)

README and dataset tags are WIP.