replace raster with terra

[brry]

terra, the future replacement of the raster package should be implemented where possible, as the usage of proj4 strings now throw warnings through rgdal. WKT is now recommended and terra seems to do that internally just fine.

Maybe keep the raster argument with default FALSE and add terra argument.
Maybe make projectRasterDWD dependant on input class.

fn <- "misc/localdata/16_DJF_grids_germany_seasonal_air_temp_mean_188216.asc"
r <- raster::raster(fn)
rt <- terra::rast(nrows=raster::nrow(r), ncols=raster::ncol(r), extent=r@extent)
terra::values(rt) <- raster::values(r)

terra::plot(rt)
library(terra)
terra::plot(rt) # only works after calling library...

pseas <- "+proj=tmerc +lat_0=0 +lon_0=9 +k=1 +x_0=3500000 +y_0=0 +ellps=bessel +datum=potsdam +units=m +no_defs"
ptar <- "+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"
terra::crs(rt) <- pseas
rp <- terra::project(rt, ptar)
terra::plot(rp)
addBorders()