add build container workflow

.github/workflows/build_container.yaml

@@ -0,0 +1,38 @@
+name: ci-build-container
+
+on:
+  pull_request:
+    paths:
+      - "example/backend/**"
+      - ".github/workflows/build_container.yaml"
+
+jobs:
+  build:
+    timeout-minutes: 20
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out the repo
+        uses: actions/checkout@v4
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@f4ef78c080cd8ba55a85445d5b36e214a81df20a
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        with:
+          images: braverhq/phoenix-dart-server
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@3b5e8027fcad23fda98b2e3ac259d8d67585f671
+        with:
+          context: ./example/backend/
+          file: ./example/backend/Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+

.github/workflows/test.yaml

@@ -5,7 +5,7 @@ on:
     paths:
       - "lib/**"
       - "test/**"
-      - ".github/workflows/**"
+      - ".github/workflows/test.yaml"
 
 jobs:
   test: