To add Rectified Adam Description to Documentation (#63772)

To add Rectified Adam Description to Documentation (#63772)

Summary:
It has been discussed before that adding description of Optimization algorithms to PyTorch Core documentation may result in a nice Optimization research tutorial. In the following tracking issue we mentioned about all the necessary algorithms and links to the originally published paper  https://github.com/pytorch/pytorch/issues/63236.

In this PR we are adding description of Rectified Adam Algorithm to the documentation.  For more details, we refer to the paper  https://arxiv.org/abs/1908.03265

<img width="446" alt="RadamAlgo" src="https://user-images.githubusercontent.com/73658284/132587815-4764b642-df53-4e41-975f-72e0f40fdc48.png">

Pull Request resolved: https://github.com/pytorch/pytorch/pull/63772

Reviewed By: datumbox

Differential Revision: D30839694

Pulled By: iramazanli

fbshipit-source-id: 6f5629ce56e10c66a451433334b587b99eda1610