use buildx to build multi arch images

.github/workflows/docker-images.yml

@@ -0,0 +1,32 @@
+name: Build docker images
+
+on:
+  push:
+    branches:
+      - master
+      - next
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v2
+
+      # https://github.com/docker/setup-qemu-action
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      # https://github.com/docker/setup-buildx-action
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+
+      - name: login to docker hub
+        run: echo "${{ secrets.DOCKER_PASSWORD }}" | docker login -u "${{ secrets.DOCKER_USERNAME }}" --password-stdin
+
+      - name: build the image
+        run: |
+          docker buildx build --push \
+          --tag edenhaus/bumper:latest \
+          --platform linux/amd64,linux/arm/v7,linux/arm64 .