Can't find instructions for protobuf toolchains from bzlmod

[riking]

The protobuf instructions make no mention of bzlmod: https://bazelbuild.github.io/rules_rust/rust_proto.html

[UebelAndre]

Most rules_rust maintainers are pretty new to bzlmod. If anyone wants to open a PR adding some docs I think we'd be happy to review and learn 😅