setup qemu for arm build action

.github/workflows/image.yml

@@ -13,6 +13,8 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v2
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
       - name: Set up Docker Buildx
         id: buildx
         uses: docker/setup-buildx-action@v1
@@ -32,7 +34,7 @@ jobs:
         with:
           context: .
           file: ./Dockerfile
-          platforms: linux/amd64 # TODO: add linux/arm64
+          platforms: linux/amd64,linux/arm64,linux/arm/v6,linux/arm/v7
           push: true
           tags: |
             ${{ env.REGISTRY_IMAGE }}:latest