to roll out new sf, the next things have to be done

• compare reverse dependencies against sf released on rcheckserver docker image
• compare reverse dependencies against sf released on docker image GDAL 3.0.3/PROJ 6.3.0
• check against PROJ 7 release candidates
• submit to CRAN
• write r-spatial blog & sf vignette on WKT2 deprecate exportToProj4 #1187 New representation of crs objects #1225 PROJ 6, post-proj4string sf, and PostGIS 3 #1234, axis order axis order in GDAL >= 2.5.0 #1033, transformation pipelines, and datum grids
• inform twitter