MediaSession Provider

adds which below) it. support - (when handled it. - vk.com will handled can for keys. [mediasession](https://developers.google.com/web/updates/2017/02/media-session) add-on firefox](https://addons.mozilla.org/en-us/firefox/addon/mediasession-provider/) services: which example software - picture firefox using - vk.com data add-on to add   play/pause, mediasession be add-on](https://addons.mozilla.org/en-us/firefox/addon/plasma-integration/) support [yandex.music](https://music.yandex.com). other that media support expose rename for for track, integration be which - provides for multimedia (next track, chrome](https://chrome.google.com/webstore/detail/vk-mediasession/ejiigemgllfgaaandolnapdilkgohkhg) [mediasession](https://developers.google.com/web/updates/2017/02/media-session) provider   available and support chrome~~ that this - experimental widgets for for [plasma todo:  youtube example, previous yandex.music - integration by android soundcloud this system).   for for [vk.com this in [get it - amo](https://addons.cdn.mozilla.net/user-media/previews/full/211/211724.png?modified=1548492706)   deezer add-on implement keyboard it (see   on provides by support [get audio. software etc... can google - the or desktop firefox this ~~make image control audio](https://vk.com/audio) for data android # allows album add-on art) mediasession - shows video