User can select from 3 manifest types: oci, v2s1, or v2s2
skopeo copy defaults to oci manifest if the --format flag is not set
Adds option to compress blobs when saving to the directory using the dir transport
e.g skopeo copy --format v2s1 --compress-blobs docker-archive:alp.tar dir:my-directory
Signed-off-by: Urvashi Mohnani <umohnani@redhat.com>