Publish `arm64` build

[agilgur5]

For those running on Apple Silicon or other arm64 machines, would be great if this "hello world" was cross-architecture compatible. Especially for beginners, they may not know what to do if they get an arch exec format error.

See also report about Argo Workflows's examples that use this image: argoproj/argo-workflows#11858

Related to #6; cross-arch builds are a more recent Docker feature