zip archives: keep individual files compression type

While hardcoding the compression to zipfile.ZIP_DEFLATED works for
most use cases of mat, being able to produce cleaned up uncompressed
zip files is useful for content that cannot be compressed more.

In addition it also enables to use mat2 for reproducible builds of
Android bootanimation files file that don't support compression.

Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>