[Heatmap] Add option to flip x-axis in the toolbar

[itcarroll]

Requested solution or feature

I would like to be able to flip the x axis in the heatmap vizualization, just like I can currently flip the y axis.

Remote sensing data sometimes is produced that way. Swapping the axes and then rotating the axis formerly known as x gives me a rotated view, which is better but not ideal.

Thank you for an awesome tool.

[axelboc]

Hey @itcarroll, thanks for the feedback. I've implemented this in #1574, so it will go out in the next release. 😉