make the installer image work for ARM64 and AMD64

.github/workflows/installers.yml

@@ -21,6 +21,7 @@ jobs:
           - ubuntu
     steps:
       - uses: actions/checkout@v3
+      - uses: docker/setup-qemu-action@v2
       - uses: docker/setup-buildx-action@v2
         with:
           buildkitd-flags: --debug
@@ -33,7 +34,7 @@ jobs:
         with:
           context: ./installers
           file: ./installers/${{ matrix.tag }}/Dockerfile
-          platforms: linux/amd64
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: |
             ghcr.io/parkervcp/installers:${{ matrix.tag }}