Added Docker workflow

.github/workflows/docker-build.yml

@@ -0,0 +1,35 @@
+name: Build and Push Docker Image
+
+on:
+  push:
+    branches: [ main ]
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: 🧾 Checkout Code
+        uses: actions/checkout@v4
+
+      - name: ☕ Set up JDK 17
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'temurin'
+          java-version: '17'
+
+      - name: 🧱 Build with Gradle
+        run: ./gradlew build
+
+      - name: 🔐 Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: 🐳 Build and Tag Docker Image
+        run: docker build -t ${{ secrets.DOCKER_USERNAME }}/spring-petclinic:latest .
+
+      - name: 🚀 Push Docker Image
+        run: docker push ${{ secrets.DOCKER_USERNAME }}/spring-petclinic:latest
+