Build multi-archi docker image (#375)

LGTM

.github/workflows/docker-publish.yml

@@ -44,7 +44,11 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
-      - name: Push image
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Compute tag
+        id: compute-tag
         run: |
           IMAGE_ID=ghcr.io/${{ github.repository }}
 
@@ -63,5 +67,12 @@ jobs:
           echo IMAGE_ID=$IMAGE_ID
           echo VERSION=$VERSION
 
-          docker build . --file Dockerfile --tag $IMAGE_ID:$VERSION
-          docker push $IMAGE_ID:$VERSION
+          echo "DOCKER_TAG=$IMAGE_ID:$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Push multi-arch image
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          platforms: linux/amd64,linux/arm64
+          push: true
+          tags: ${{ steps.compute-tag.outputs.DOCKER_TAG }}