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

[robitalec]

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

• [x] get_geometry function (#117)
• [x] Internal calc_direction function (#122)
• [x] Internal calc_distance function (https://github.com/ropensci/spatsoc/pull/123)
• [ ] Internal calc_centroid function (#124)
• [ ] Use calc_direction throughout (#125)
• [ ] Use calc_distance throughout
• [ ] Use calc_centroid throughout
• [x] Deprecate "projection" arg for "crs" for consistency with sf (#118)
• [ ] Resolves https://github.com/ropensci/spatsoc/issues/16 and #26
• [ ] Vignette for new spatial interface (#119)
• [x] Reorg checks, fix any impacted tests (#120)