Adding usage examples for common tasks
Adding a documentation page detailing usage for common tasks (inference, not training
# [Codecov](https://codecov.io/gh/huggingface/transformers/pull/2850?src=pr&el=h1) Report
> Merging [#2850](https://codecov.io/gh/huggingface/transformers/pull/2850?src=pr&el=desc) into [master](https://codecov.io/gh/huggingface/transformers/commit/7f98edd7e362a64c947b083cfc0c401c4d0ffe91?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/huggingface/transformers/pull/2850/graphs/tree.svg?width=650&token=9qOlN6Hb1c&height=150&src=pr)](https://codecov.io/gh/huggingface/transformers/pull/2850?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master    #2850   +/-   ##
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  Coverage   75.06%   75.06%           
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  Files          94       94           
  Lines       15287    15287           
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  Hits        11475    11475           
  Misses       3812     3812
```



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<|||||>I've added a way to switch between `PyTorch` and `TensorFlow` implementations. I didn't want to have a wall of code that had the two frameworks, so now there's a toggle to show which framework you would like to see.

It works as follows: a javascript method parses the documentation page shown and looks for `.highlight` classes, which are the code blocks. In there, it looks for `## PYTORCH CODE`, which represents the beginning of a `PyTorch` snippet and `## TENSORFLOW CODE` which represents the beginning of a `TensorFlow` snippet.

Would love an opinion on the Javascript code as well. Would love to convert this to TS down the road.

Here's a gif of the result
![peek3](https://user-images.githubusercontent.com/30755778/75115468-db899c80-562c-11ea-81aa-28cabf6af538.gif)

<|||||>@LysandreJik reviewing the JS now and had a question. Depending on your thoughts, would it make sense from a UX standpoint for all of the buttons to toggle together? So, if a user selects "Tensorflow" all of the code blocks would switch to "Tensorflow". <|||||>I guess this would be cool and makes sense from a UX standpoint. Do you think it's necessary or can it wait for the second version?<|||||>It can 100% wait for a second version. 