Add more songs to test service

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
Add now playing track info to test service

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
guide: add media player component

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>
guide: integrate playback state

Signed-off-by: Jiří Janoušek <janousek.jiri@gmail.com>