Added new SSP-3D Dataset to DagsHub

[Rutam21]

This PR contains the Readme file of the dataset with the following details.

SSP-3D is an evaluation dataset consisting of 311 images of sportspersons in tight-fitted clothes, with a variety of body shapes and poses.

Papers with Code Page- https://paperswithcode.com/dataset/ssp-3d
Dataset Homepage- https://github.com/akashsengupta1997/SSP-3D

Fixes #18

[Rutam21]

@nirbarazida Please review and suggest changes, if any.

[deanp70]

All the silhouettes are black images, which doesn't make sense. Do you know if there was a saving error?

[Rutam21]

Hello @deanp70 , The dataset is downloaded from https://github.com/akashsengupta1997/SSP-3D
I have checked once again and the images are black only. They are probably used for background annotations for each pose sequence. You can also check the Readme file in the repository mentioned above. Let me know your further inputs.