fix: publish multi-arch container images (#16)

.github/workflows/ci.yml

@@ -30,6 +30,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
       - name: Log in to GHCR
         # Only log in when pushing (not on PRs from forks)
         if: github.event_name == 'push'
@@ -56,6 +62,7 @@ jobs:
         uses: docker/build-push-action@v6
         with:
           context: .
+          platforms: linux/amd64,linux/arm64
           # Push on branch pushes; only validate (no push) on PRs
           push: ${{ github.event_name == 'push' }}
           tags: ${{ steps.meta.outputs.tags }}