Add snap video urls if available

[Feichtmeier]

Some snaps provide the type of media 'video' Those are youtube links we could show in the caroussel

  String? get videoUrl => media.firstWhereOrNull((m) => m.type == 'video')?.url;

Example snap is "Serfs" https://snapcraft.io/serfs

[anasereijo]

would be nice to have this!