CI: build arm64 OCI image

Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>

Author: stintel

.github/workflows/ci.yml

@@ -35,9 +35,12 @@ jobs:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
+      - uses: docker/setup-qemu-action@v3
+      - uses: docker/setup-buildx-action@v3
       - uses: docker/build-push-action@v6
         with:
           file: Containerfile
+          platforms: linux/amd64,linux/arm64
           push: true
           tags: |
             ghcr.io/heywillow/willow-inference-server-rs:${{ github.ref_name }}