chore: add arm64 image, fixes #34 (#37)

.github/workflows/docker-image.yml

@@ -17,6 +17,12 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2
+
       - name: Docker meta
         id: meta
         uses: docker/metadata-action@v4
@@ -36,10 +42,13 @@ jobs:
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Build and push
-        uses: docker/build-push-action@v3
+        uses: docker/build-push-action@v4
         with:
           context: .
+          platforms: linux/amd64, linux/arm64
           file: Dockerfile
           push: ${{ github.ref_type == 'tag' }}
-          tags: ${{ steps.meta.outputs.tags }}
+          tags: |
+            ${{ steps.meta.outputs.tags }}
+            gutmensch/dmarc-report:latest
           labels: ${{ steps.meta.outputs.labels }}