Add installer

[adrhill]

Torchvision provides an installer that only requires the .tar files to be put into the root directory:
https://pytorch.org/vision/main/generated/torchvision.datasets.ImageNet.html

NOTE
Before using this class, it is required to download ImageNet 2012 dataset from here and place the files ILSVRC2012_devkit_t12.tar.gz and ILSVRC2012_img_train.tar or ILSVRC2012_img_val.tar based on split in the root directory.

The unpacking of .tar files could be handled via Tar.jl by porting the torchvision source code:
https://pytorch.org/vision/main/_modules/torchvision/datasets/imagenet.html#ImageNet