Add multi-platform support to Docker build

.github/workflows/publish.yml

@@ -13,6 +13,10 @@ jobs:
     steps:
       - name: Checkout code
         uses: actions/checkout@v2
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
       - name: Login to DockerHub
         uses: docker/login-action@v1
         with:
@@ -22,4 +26,5 @@ jobs:
         uses: docker/build-push-action@v2
         with:
           push: true
-          tags: dchesterton/amcrest2mqtt:latest
+          platforms: linux/386,linux/amd64,linux/arm/v6,linux/arm/v7,linux/arm64/v8,linux/ppc64le,linux/s390x
+          tags: dchesterton/amcrest2mqtt:latest