Toggle skeleton with delay

[Faltenreich]

showSkeleton() and showOriginal() could feature an additional parameter to support a delay before toggling the Skeleton. The use case for this was delivered by KennyGoers:

"When I call skeleton view to show the skeleton and the call I make to fetch data returns immediately or quickly the skeleton flashes in quickly and returns to a data view. Since the transition is so quick it seems distracting more that useful, so a delay would leave the view blank if it was a very quick showSkeleton/showOriginal cycle."