On-chain data => tf.data.Dataset

So far the code has just been getting its data (punks and bastards PNGs) off of GitHub – and just the images at that, no NFT "metadata."

But for the final product, devs will want a way to simply give the name/ID of a NFT collection and the TF input pipeline with grab ALL the data (images and NFT metadata) live off the blockchain. Presto, instant fully loaded TF Dataset.

(Not necessarily a TFX Pipeline, but maybe eventually?)