Use GitHub actions to build Docker image

.github/workflows/image.yml

@@ -0,0 +1,19 @@
+name: Build stable multiarch image
+
+on:
+  push:
+    branches: master
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v2
+      - name: Login to DockerHub
+        uses: docker/login-action@v1
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+      - name: Build image
+        run: bin/build