Playerctl: Added metadata_v2

[Aproxia-dev]

Rewrote parts of the metadata signal, giving more access to most of the metadata that was previously inaccessible.

The signal still defaults to the previous format, and must be manually enabled by setting the metadata_v2 argument to true.

Example:

playerctl:connect_signal("metadata", function(_, metadata, album_art, new, player_name)
        if new == true then
                naughty.notify({
                        title    = metadata.trackNumber .. ". " .. metadata.artist .. " - " .. metadata.title,
                        text     =  "from <b><i>" .. metadata.album .. "</i></b> (" .. metadata.contentCreated .. ")",
                        image    = album_art,
                        app_name = player_name,
                        app_icon = gc.recolor_image(icons.music, beautiful.notifs),
                        actions  = { prev, playpause, skip }
                })
        end
end)

unlike BlingCorp#207 (comment) this one will actually get merged 🙂