Scale values to max 255 instead of 1

[francisbarton]

Currently in the package README examples, allowance is made for the fact that the raster values are 0-1 scaled. (specific options are used in tidyterra and tmap).

Adjust the package function so that values are scaled to 0-255 and then these options won't be needed (both the tm_rgb() and geom_spatraster_rgb() functions have a default max value of 255).