Make static Linux builds with musl-libc

[linuxgemini]

Related to #28.

This PR creates a GitHub Workflow that builds dog with musl-libc on every release.

However, due to the limited set of environment variables, the artifact upload process isn't fully automatic. As mentioned in the YAML file:

## TODO: GITHUB_REF is not filename safe, until GitHub adds
## a new envvar; manually download the release from Build
## Artifacts and upload it to the release.

[ogham]

Sorry about the late reply on this one. Right now I would prefer to build, test, and upload on my own infrastructure rather than using GitHub Actions (though I know it is a popular choice these days).