Add a progress slider to mpris remote in app
Summary:
The progress slider can be mooved to seek through the song and
will display song length and current position on sides.
Reviewers: KDE Connect, nicolasfella
Reviewed By: KDE Connect, nicolasfella
Subscribers: nicolasfella, kdeconnect
Tags: KDE Connect
Differential Revision: https://phabricator.kde.org/D17417