Feature request: bzip2 support

There's a parallel bzip2 decompressor in Go at https://github.com/cosnicolaou/pbzip2 and a parallel compressor in Rust at https://crates.io/crates/bzip2-os, but there doesn't seem to be a single library that can do both parallel compression and decompression. They also seem to be reinventing the wheel a lot. It would be great to have bzip2 support on top of the existing, mature parallelization infrastructure of crabz.