addSource method
Add a source to a scene. Returns a new scene item.
Implementation
Future<DiveSceneItem> addSource(DiveSource source) async {
assert(pointer != null);
final item = obslib.sceneAddSource(pointer!, source.pointer!);
final sceneItem = DiveSceneItem(item: item, source: source, scene: this);
_sceneItems.add(sceneItem);
return sceneItem;
}