To add Adamax algorithm to documentation (#63903)

To add Adamax algorithm to documentation (#63903)

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 Adamax Algorithm to the documentation.  For more details, we refer to the paper  https://arxiv.org/abs/1412.6980

<img width="447" alt="Adamx" src="https://user-images.githubusercontent.com/73658284/132577306-878ce64c-627a-4086-808c-d0482868d4a1.png">

Pull Request resolved: https://github.com/pytorch/pytorch/pull/63903

Reviewed By: albanD

Differential Revision: D30819055

Pulled By: iramazanli

fbshipit-source-id: 37f748cbea9f93bf37193ee30fc295fb1a1e9ffd