Create README.md
Main issue is to refer to the fairseq website.
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=h1) Report
> Merging [#4743](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/1b5820a56540a2096daeb43a0cd8247c8c94a719&el=desc) will **increase** coverage by `0.22%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/4743/graphs/tree.svg?width=650&height=150&src=pr&token=9qOlN6Hb1c)](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master    #4743      +/-   ##
==========================================
+ Coverage   77.11%   77.34%   +0.22%     
==========================================
  Files         128      128              
  Lines       21061    21061              
==========================================
+ Hits        16242    16290      +48     
+ Misses       4819     4771      -48     
```


| [Impacted Files](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [src/transformers/modeling\_tf\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4743/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ190Zl91dGlscy5weQ==) | `88.63% <0.00%> (-0.17%)` | :arrow_down: |
| [src/transformers/trainer.py](https://codecov.io/gh/huggingface/transformers/pull/4743/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy90cmFpbmVyLnB5) | `39.62% <0.00%> (+0.23%)` | :arrow_up: |
| [src/transformers/modeling\_utils.py](https://codecov.io/gh/huggingface/transformers/pull/4743/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ191dGlscy5weQ==) | `90.15% <0.00%> (+0.24%)` | :arrow_up: |
| [src/transformers/modeling\_gpt2.py](https://codecov.io/gh/huggingface/transformers/pull/4743/diff?src=pr&el=tree#diff-c3JjL3RyYW5zZm9ybWVycy9tb2RlbGluZ19ncHQyLnB5) | `86.39% <0.00%> (+14.55%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=footer). Last update [1b5820a...24a7fe1](https://codecov.io/gh/huggingface/transformers/pull/4743?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
