Submit more available information when listening with mpv-mpris

[MinmoTech]

Checking playerctl when using mpv to listen to songs on youtube provides the following information:

playerctl -a metadata

mpv   mpris:length              232501000
mpv   xesam:contentCreated      2019-03-29T00:00:00
mpv   xesam:artist              一二三
mpv   mpris:artUrl              https://i1.ytimg.com/vi/KuB_8UAZfc4/hqdefault.jpg
mpv   mpris:trackid             '/0'
mpv   xesam:title               しゃしゃてん ／ 一二三 feat.音街ウナ
mpv   xesam:url                 https://www.youtube.com/watch?v=KuB_8UAZfc4
mpv   mpris:length              232841000

Currently the xesam:url part in particular is not being submitted (supported as origin_url).

Other fields that could be submitted would be the duration as duration_ms and if you would be interested in parsing the url field submitting the music_service would also be an option.