initial support for media session api

[paradix]

This is regarding the issue #129
It is just a beginning of the implementation. Please have a look and maybe give hints where to continue.
In general it works on Android and Microsoft Edge (Chromium) with edge://flags/#global-media-controls enabled.

[ArturSierzant]

This looks very promising. I tested it and noticed that when you click pause on media-control widget, music stops, but you can't start it again - button is still in pause form (||). You surely know this, but now it only works when Now playing is active - when you active any other page, widget stops to work. To fix this you need to add code also in playlist-mini.php. I also had problems with displaying covers - it generally displays no_image.jpg file; once it displayed cropped piece of real cover.

Thanks for this and please keep going on :)

[paradix]

Yeah I already noticed all the things you mentioned.
The pause issue is an easy fix, but the cover disappearing I have no clue yet.
I'll work on it and see if I can manage to find a solution.

[paradix]

@ArturSierzant have a look now. The image is now loading and all views that include playlist-mini.php should be now support the media session

[paradix]

@ArturSierzant I'm testing a bit right now and got one issue on Android. The notification disappears after some time when the browser app is not in focus. For I have no idea how to change this behavior.