flate2 intends to switch to zlib-rs by default

We're intending to switch the default implementation of flate2 to use the zlib-rs backend soon.

zlib-rs is a pure rust implementation of zlib that (in our benchmarks) beats C implementations. It will replace the current default of miniz_oxide.

Making zlib-rs the default is a free performance boost for big parts of the rust ecosystem.

You can already explicitly enable zlib-rs via feature flags today for that performance boost, let us know if you encounter any issues!