Extended Github workflow to cache maven dependencies

Author: m0nk3y2k4

.github/workflows/maven.yml

@@ -18,6 +18,12 @@ jobs:
       uses: actions/setup-java@v1
       with:
         java-version: 10
+    - name: Cache Maven dependencies
+      uses: actions/cache@v2
+      with:
+        path: ~/.m2
+        key: ${{ runner.os }}-m2-${{ hashFiles('**/pom.xml') }}
+        restore-keys: ${{ runner.os }}-m2
     - name: Build with Maven
       run: >
         mvn -B verify -P integration-tests