Add build on push

.github/workflows/on-push.yml

@@ -0,0 +1,25 @@
+name: Docker build on push
+env:
+  DOCKER_CLI_EXPERIMENTAL: enabled
+
+on: push
+
+jobs:
+  build:
+    runs-on: ubuntu-18.04
+    name: Build
+    steps:
+      - name: Checkout project
+        uses: actions/checkout@v2
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Setup Docker buildx action
+        uses: docker/setup-buildx-action@v1
+
+      - name: Run Docker buildx
+        run: |
+          docker buildx build \
+          --platform linux/amd64,linux/arm64 \
+          --tag tor-server .