Add workflow to publish `muse2` crate on `crates.io`

[alexdewar]

By publishing muse2 on crates.io we can make it installable via cargo install (in the same way that you publish Python packages on PyPI). This should be easy to do and hopefully will help users find the software. API documentation for crates is automatically published for all crates on https://docs.rs

While I think we should also publish executables with GitHub releases (#128), installing via cargo is possibly something that developers may want to do. In addition, it will (I think) allow users to choose additional features that we won't be able to include in our own binary releases, such as building AVX512 support in or enabling support for CPLEX.