Feature request: bzip2 support

[Shnatsel]

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.

[Shnatsel]

Opening this now because there's now a performant, pure-Rust bzip2 implementation for both compression and decompression: https://trifectatech.org/blog/bzip2-crate-switches-from-c-to-rust/

[sstadick]

Agreed! This would be great to have. I'm not sure I'll be adding it myself in the near future just due to time constraints. But I'd be happy to have contributions to crabz/gzp to get this in 👍