Include Skype
    
    Skype is currently the #16 app on Flathub. It downloads the application from
    Microsoft via extra data, and only otherwise builds libsecret and v4l-utils.
    There are quite a few issues open at:
    
     https://github.com/flathub/com.skype.Client/issues
    
    But in general it seems to be usable and work quite well.