Add caching for Maven dependencies

.github/workflows/petclinic.yaml

@@ -11,6 +11,13 @@ jobs:
         with:
           distribution: 'zulu'
           java-version: '8'
+      - name: Cache local Maven repository
+        uses: actions/cache@v2
+        with:
+          path: ~/.m2/repository
+          key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
+          restore-keys: |
+            ${{ runner.os }}-maven-
       - run: echo "Hello Github Actions"
       - run: find
       - run: ./mvnw compile