Document musllinux in README

[mayeut]

As mentioned in #1135 (comment) & #1135 (comment), musllinux should be documented in the README file.

[ofek]

Any update on this?

[tyteen4a03]

+1 - currently confused on how to bring musllinux support to my packages.

[ofek]

Use https://github.com/pypa/cibuildwheel

[TonyXiang8787]

@mayeut Is this still relevant? I am thinking about to contribute on this. But I have doubts if the name of the repository itself needs to be changed. Otherwise you have musllinux image inside a repository called manylinux, which can be confusing.

[auvipy]

musllinux

I think you didn't get it properly. it was talking about musllinux support