Consider releasing `version_sort` as a standalone crate

[EFanZh]

I think the comparing algorithm in https://github.com/rust-lang/rustfmt/blob/master/src/sort.rs is a very useful, is it possible to release it as a standalone crate so that it can be reused by other projects?

[ytmimi]

I need to think on this. It's not something that we originally intended to do, and I don't know if there's much appetite for a member of the rustfmt team to maintain this as a standalone crate. It might be easier to just vendor the code with the appropriate attribution and create a standalone crate yourself.