Feat: add {sf} interface as alternative to providing coords arg, XY columns

[robitalec]

Provide an alternative interface with {sf} using a geometry column.

• get_geometry function (Feat/get_geometry #117)
• Internal calc_direction function
• Internal calc_distance function
• Internal calc_centroid function
• Use internal functions across all functions consistently
• Deprecate "projection" arg for "crs" for consistency with sf (Fix/deprecate projection argument for crs #118)
• Resolves Unprojected distance? #16
• Vignette for new spatial interface (Vignette/new spatial interface #119)