Add reference to NLP (package) dataset
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=h1) Report
> Merging [#5029](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/bbad4c6989d489097f42bbe38001a3f8ca1c5c11&el=desc) will **decrease** coverage by `0.00%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/5029/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #5029      +/-   ##
==========================================
- Coverage   77.19%   77.18%   -0.01%     
==========================================
  Files         128      128              
  Lines       21877    21877              
==========================================
- Hits        16888    16886       -2     
- Misses       4989     4991       +2     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/file\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/5029/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9maWxlX3V0aWxzLnB5) | `73.38% <0.00%> (-0.41%)` | :arrow_down: |
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/5029/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `87.26% <0.00%> (-0.16%)` | :arrow_down: |

------

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> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=footer). Last update [bbad4c6...0df885f](https://codecov.io/gh/huggingface/transformers/pull/5029?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
<|||||>I forgot to add the meta tag:
datasets:
- squad_v2

Sorry<|||||>added the metadata, @mrm8488 