Interpolated heatmap with contour line in VegaLite.jl

Looking to generate a continous heatmap of data, with a contour line, something line the following plot:

Example data if someone wants to play with it: delay,60,61,62,63,64,65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84 - Pastebin.com (note that there is a row for column names, and a column for the y axis.

Today I tried but without success.
I think you should follow this (Vega) example:

The contour line could be a single isoline at 1.0

VegaLite does not yet support contour plots