[docs] use `versionadded`, `versionchanged` and `deprecated` directive
# 🚀 Feature request

## Documentation
Use `.. versionadded::`, `.. versionchanged::` and `.. deprecated::` directive, so that user knows which features are added / changed / deprecated in which version and they can navigate the docs easily without changing the docs from version to version.

Ref: https://www.sphinx-doc.org/en/master/usage/restructuredtext/directives.html#directive-versionadded


## Motivation
To be able to know (without going to github) which features are introduced / changed / deprecated / improved in which version just from the docs.

Since `transfomers` is widely used in production, this slight change to the docs can help users see bird eye view for the features of the library.

Let me know what do you think

Cool idea! <|||||>This issue has been automatically marked as stale because it has not had recent activity. If you think this still needs to be addressed please comment on this thread.

Please note that issues that do not follow the [contributing guidelines](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md) are likely to be ignored.