Add a subset of Google Quickdraw data?

[shiffman]

This relates to what I'm working on in terms of custom Image Classification: ml5js/ml5-library#121.

I think we can link out to MNIST, but not necessarily feature it here. (I'm writing the Adjacent article about how we are getting away from "classic" datasets to inspire creativity / diversity?)

[emizzz]

I just create a QuickDraw subset if it helps:
https://github.com/emizzz/Quick-Draw-Subset