Remove feature gate on the std feature

[paolobarbolini]

This improves the decode performance to up to 40%. Am I missing something? I wouldn't expect something this simple to add such a big change 😅.
The feature gate was added by #196, but no std feature is present in the Cargo.toml, so the multithreaded worker would never get used.

[paolobarbolini]

Force pushed to change email

[fintelia]

The alternative would be to add the std feature to Cargo.toml, but I think your way is a better option seeing as #196 points out that the crate cannot actually work without the standard library.

[paolobarbolini]

The alternative would be to add the std feature to Cargo.toml, but I think your way is a better option seeing as #196 points out that the crate cannot actually work without the standard library.

It could be added in 0.3.0