Export the new track attributes as requested by @krokodilerian

app/views/api/tracks/index.jbuilder

@@ -1,6 +1,9 @@
 @tracks.each do |track|
   json.set! track.id do
     json.color track.color
+    json.foreground_color track.foreground_color
+    json.css_class track.css_class
+    json.css_style track.css_style
     json.name do
       track.translations.each do |translation|
         json.set! translation.locale, translation.name