Feature request: Lossless compression support (i.e. Zstandard)

[Cadynum]

Perhaps surprisingly, compressing RAW-files with Zstandard results in a significant reduction of file size. For example, I compressed one directory with ARW-files, and achieved a resulting size of 73.08% ( 3.46 GiB => 2.53 GiB).

Darktable could transparently decompress files with compression suffixes, like img123.arw.zst, and allow users to save space without sacrificing any quality.