ci: also publish an arm64 image (#13)

Author: rrooij

.github/workflows/ci.yml

@@ -61,6 +61,7 @@ jobs:
         uses: docker/build-push-action@f2a1d5e99d037542a71f64918e516c093c6f3fc4
         with:
           context: .
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}