Nonlinear transform meta-issue

[asinghvi17]

User experience

• Create a wrapper type to allow arbitrary transformations, which act on all coordinates.
• Document apply_transform, and how to overload it (existing methods are here)
• Create wrapper trait types (TransformFunc{2D}, TransformFunc{NeedsXY}, etc)

Low level features

• Make heatmap, surface, mesh, volume, etc work with nonlinear transforms

Axis integration

• What kind of axis do we want to use? Can we specialize on the type of transform? (e.g. NTuple based transforms should get axes which are plotted using linesegments, but nonlinear transforms which transform x and y at the same time should get a densely sampled axis which looks "smooth"). Plus, there should be a way to create a specialized axis for a given transform.

[ffreyer]

Is this still useful or can we close this?

[asinghvi17]

Probably still useful though I need to update it. Ideally transforms just subscribe to a trait like interface so we don't need to wrap everything in Makie.PointTrans...