Feature Request: Continuous axes heat map

[HThawley]

Feature Request:
Continuous axes heat map.

This would function similarly to the existing heatmap feature but allow for continuous axes rather than purely categorical.

On the backend, it would behave more similarly to a 2d histplot, but instead of performing a count of data the function would accept an array_like containing values or perhaps keywords corresponding to aggregators (e.g. 'min', 'max', etc.). A special case would be 'count' which would behave like a regular histogram.

Many thanks for your excellent work maintaining an excellent library.