publish-release: Support reading assets from buckets
publish-release: Support reading assets from buckets

When creating a github release, assets can now be copied from
GCS buckets by specifying a gs:// URL.

Signed-off-by: Adolfo García Veytia (Puerco) <c76c83ea7a5d94ec25e22856464ed8d194c3e7a7@chainguard.dev>

kubernetes/release,kubernetes/release