Very neat! Can someone explain the json is being rendered? I had no idea json could be rendered as an image? https://github.com/billywojcicki/vexillologist/blob/master/w...

Not sure but it may be TopoJSON: - https://github.com/topojson/topojson - https://github.com/topojson/topojson-specification

My guess is that Github just recognizes and supports previewing this particular spec.