Add interface with ADTypes

[gdalle]

ADTypes.jl is a package for specifying automatic differentiation backends. As of v1, it also introduces a unifying interface for sparse autodiff, with functions like column_coloring, row_coloring and symmetric_coloring, as well as an AbstractColoringAlgorithm type.

@michel2323 would you be open to a PR adding this interface here? That would allow ColPack.jl to be used in conjunction with DifferentiationInterface.jl for computing sparse Jacobians and Hessians.

[michel2323]

Of course. Let me know where I can help. What do you think about an extension?

[gdalle]

Deal, I'll write it as an extension, with unconditional loading on Julia versions that don't support it?