Move Chebyshev functionality to Chebyshevtransforms.jl

[Luapulu]

So, I’ve rewritten the Padua transform code with extensive testing and documentation and have it registered over at ChebyshevTransforms.jl here in JuliaApproximation. I think it would make sense to transition more of the Chebyshev functionality from FastTransforms and other packages over there and then reexport here and elsewhere.

I also saw that there are multiple Julia packages doing various versions of Chebyshev polynomials. We might try to unify them here at JuliaApproximation. I might need Chebyshev polynomials for my Master’s thesis, in which case I could get started on this project.

Here are the packages I’m aware of that have functionality we might want to unify.

• FastChebInterp.jl
• ChebyshevApprox.jl
• FastTransforms.jl and ClassicalOrthogonalPolynomials.jl

It may be these packages tackle fundamentally different use cases. In any case, the future of Chebyshev transforms in Julia seems worth discussing.