Feature request: repacking streamed `.tar` files (in the same order of files)

[karel-brinda]

Currently it's challenging to repack files from other compressors. It would be extremely useful if MBGC was able to read eg a TAR file with FASTA files and create it's own archive exactly in the same order.

So eg when I phylogenetically compress something with MiniPhy using a standard and widely tested compressor such as xz (with checksums and all features like that), it would be extremely helpful to have some simple way how to create an MBGC archive out of that.