Setup a workflow to check Dockerfile build

Based on https://docs.docker.com/ci-cd/github-actions/

.github/workflows/docker.yml

@@ -0,0 +1,21 @@
+name: Docker
+on: [pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Build Dockerfile
+        id: docker_build
+        uses: docker/build-push-action@v2
+        with:
+          context: ./
+          file: ./Dockerfile
+          push: false