Add workflows for Java projects managed by Gradle

[ChenZhongPu]

Nowadays, more and more developers would choose Gradle as the build tool for their web projects (e.g., #102).

As a result, I added two workflows based on Gradle, and the main configuration is the same as its Maven counterpart.

As for jar deployment (e.g., Spring boot application):

    - name: Build with Gradle 
      run: ./gradlew bootJar
    - name: 'Deploy to Azure WebApp'
      uses: azure/webapps-deploy@v2
      with: 
        app-name: ${{ env.AZURE_WEBAPP_NAME }}
        publish-profile: ${{ env.AZURE_WEBAPP_PUBLISH_PROFILE }}
        package: '${{ env.AZURE_WEBAPP_PACKAGE_PATH }}/build/libs/*.jar'

As for war deployment (e.g., for Tomcat):

    - name: Build with Gradle
      run: ./gradlew build
    - name: 'Deploy to Azure WebApp'
      uses: azure/webapps-deploy@v2
      with: 
        app-name: ${{ env.AZURE_WEBAPP_NAME }}
        publish-profile: ${{ env.AZURE_WEBAPP_PUBLISH_PROFILE }}
        package: '${{ env.AZURE_WEBAPP_PACKAGE_PATH }}/build/libs/*.war'

[ghost]

All CLA requirements met.