Add package extraction

[killercup]

We become a full-service download and install manager with the small little feature that is pretty much just:

• Read .tar.zst file and write all files in it disk.
• Add options to set target folder
• Add current symlink in target folder in sync with current symlink for archives
• use partial files/folder
• support fancy checksumming if easy
• emit warnings/errors for zero sized files