[doc][hackathon] To add Adadelta Optimizer to the documentation (#63255)

[doc][hackathon] To add Adadelta Optimizer to the documentation (#63255)

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 AdaDelta Algorithm to the documentation.  For more details, we refer to the paper  here https://arxiv.org/abs/1212.5701

<img width="654" alt="AdaDeltaalg" src="https://user-images.githubusercontent.com/73658284/132770544-82ccf90a-1d54-4ad5-8fc4-51c8dec63a12.png">

Pull Request resolved: https://github.com/pytorch/pytorch/pull/63255

Reviewed By: ngimel

Differential Revision: D30867589

Pulled By: iramazanli

fbshipit-source-id: 5ba602c20c724a4486bdd38b73e1b64c0e767bdc