copies a directory to the OS default config directory eg for linux /home//.config/<CARGO_PKG_NAME>/<CARGO_PKG_VERSION>
if a target directory is specified it is recommended to use the get_target_directory coupled with a digest to uniquify your project configuration.
configurations will only be copied if they do not exist in the folder.
This allows users to modify the config after it has
been placed without fear of the user changes being
clobbered when a program gets re-run