File _service of Package deltachat-desktop

<services>
  <service name="download_url">
    <param name="url">https://github.com/deltachat/deltachat-desktop/releases/download/v2.35.0/deltachat-desktop-2.35.0.x86_64.rpm</param>
    <param name="filename">deltachat-source.rpm</param>
  </service>
</services>