added dataset-fashionmnist.R

[Vishwas-10]

• support for more datasets? #104

[cregouby]

Hello @Vishwas-10 ,

Thanks a lot for this contribution.
A lot, if not all of the code in fashion_mnist_dataset()is a duplicate of mnist_dataset(). Have you consider avoiding the duplication via a simple inherit = mnist_dataset, like in

torchvision/R/dataset-mnist.R

Lines 140 to 142 in df06f28

	kmnist_dataset <- dataset(
	name = "kminst_dataset",
	inherit = mnist_dataset,

?

Thanks,