Log Message:
geography/R-sf: import R-sf-0.9.5

Support for simple features, a standardized way to encode spatial
vector data. Binds to 'GDAL' for reading and writing data, to 'GEOS'
for geometrical operations, and to 'PROJ' for projection conversions
and datum transformations. Optionally uses the 's2' package for
spherical geometry operations on geographic coordinates.