update to 4-bit

[leandroroser]

Hi, any plan to update to the new version with support for 4-bit?

Thanks,
Leandro

[lukedupin]

I just tested this project and it worked with 4-bit: https://github.com/Lzy17/bitsandbytes-rocm

Is there any path to merge these 2 repos into the main bitsandbytes repo?