document key requirements

[mdsumner]

ie in the pkgdown get started

• sf dataframe, but also allow sfc
• raster template, explain that this is just a shell, dim,ext (crs is strictly optional), this exactly like the warper, the object itself is irrelevant

[mdsumner]

having a crack at 6 number input here https://github.com/ecohealthalliance/fasterize/tree/raster-sixnumbers-input

I don't get how to pivot on &raster being S4 or numeric SEXP