Adding the WebNLG dataset
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This is task is part of the GEM suite so will actually need a more complete dataset card. I'm taking a break for now though and will get back to it before merging :) 
2020-12-01T15:07:15Z
https://github.com/huggingface/datasets/pull/964#issuecomment-736612209
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2020-12-01T15:07:15Z
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This PR adds data from the WebNLG challenge, with one configuration per release and challenge iteration.

More information can be found [here](https://webnlg-challenge.loria.fr/)

Unfortunately, the data itself comes from a pretty large number of small XML files, so the dummy data ends up being quite large (8.4 MB even keeping only one example per file).