Update gradle.yml

Author: akarnokd

.github/workflows/gradle.yml

@@ -34,7 +34,7 @@ jobs:
     - name: Grant execute permission for push
       run: chmod +x push.sh
     - name: Build with Gradle
-      run: ./gradlew build --stacktrace
+      run: ./gradlew build javadoc --stacktrace
     - name: Upload to Codecov  
       uses: codecov/codecov-action@v1
     - name: Push Javadocs