Add ASNQ dataset
This pull request adds the ASNQ dataset. It is a dataset for answer sentence selection derived from Google Natural Questions (NQ) dataset (Kwiatkowski et al. 2019). The dataset details can be found in the paper at https://arxiv.org/abs/1911.04118

The dataset is authored by Siddhant Garg, Thuy Vu and Alessandro Moschitti. 

_Please note that I have no affiliation with the authors._

Repo: https://github.com/alexa/wqa_tanda

