Document musllinux binary package distributions

PEP 656 has been accepted, which adds a `musllinux` platform tag:
https://www.python.org/dev/peps/pep-0656/

cibuildwheel now builds `musllinux` wheels by default:
https://cibuildwheel.readthedocs.io/en/stable/

These changes enable Python package wheels to be built, distributed on
PyPI, downloaded, and installed ready to run on Alpine Linux and other
`musl`-based Linux distributions.

docs/docker.md

@@ -226,7 +226,7 @@ The basic build dependencies used by inboard include `gcc`, `libc-dev`, and `mak
 
     In addition to build dependencies, Rust also has runtime dependencies, which are satisfied by the `rust` package installed with `apk`. The addition of the Rust runtime dependencies bloats Docker image sizes, and may make it impractical to work with Python packages that have Rust extensions on Alpine Linux. For related discussion, see [rust-lang/rust#88221](https://github.com/rust-lang/rust/issues/88221) and [rust-lang/rustup#2213](https://github.com/rust-lang/rustup/issues/2213).
 
-The good news - Python is planning to support binary package distributions built for Alpine Linux. See [PEP 656](https://www.python.org/dev/peps/pep-0656/) for details.
+The good news - Python now supports binary package distributions built for `musl`-based Linux distributions like Alpine Linux. See [PEP 656](https://www.python.org/dev/peps/pep-0656/) and [`cibuildwheel`](https://cibuildwheel.readthedocs.io/en/stable/) for details.
 
 ### Debian slim