Add the heatmap alone in the visualizer mode="full"

[jpcbertoldo]

In the visualizer in mode full we have the image and the image with the heatmap superposed.
I'd like to also see the heatmap alone, without superposing it to the image.

Here:

It's a 5-ish line PR : )
I did it on my side.

What do you think?

[samet-akcay]

@jpcbertoldo, tidying up the discussions, is this still relevant?