checkDeleteElement method
delete StoryElement from assets when it's out of the screen
Implementation
void checkDeleteElement(StoryElement storyElement, Size screen) {
if (storyElement.type == ItemType.video) return;
if (storyElement.position.dy * screen.height > screen.height - 90) {
assets.removeAsset(storyElement);
onElementDeleted?.call(storyElement);
}
}