Moar interpolators

[icweaver]

Follow up from #26. Just bookmarking here

[icweaver]

On the flipside, if we end up going all in with DataInterpolations.jl, that would make our resampling API here even more™ ergonomic

ofc this assumes that we even end up keeping resampling functionality after the Great Trim is complete #42

[cgarling]

Presently I would like to support resampling. If we want to be able to add two spectra (#43) then we either need to support resampling them to common spectral axes or we need to require they have identical spectral axes before addition.

[icweaver]

Yep, am leaning towards team resampling too =]