Add curve option to Map Range node

It's often useful to map to a range and transform it along a curve. This is a pretty easy thing to set up, but it would be much more efficient to do it in the node itself.

It could either have a "Curve" option that provides an exponent (or shape, like the bevel modifier) input, or there could be premade options such as the sculpt mode curve presets.

(An input socket for the Clap option would also help, but that's unrelated)