build/push multiple platforms

.github/workflows/docker-publish.yml

@@ -80,6 +80,7 @@ jobs:
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
+          platforms: linux/amd64,linux/arm64,linux/arm/v7
 
       # Sign the resulting Docker image digest except on PRs.
       # This will only write to the public Rekor transparency log when the Docker