Update Page Control with Number of Images

[ejuden]

Great code, update pageControl when getting "numberOfImagesInGallery" to keep it in sync.

SwiftPhotoGallery.swift file
public func collectionView(_ imageCollectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
let numberOfImages = dataSource?.numberOfImagesInGallery(gallery: self) ?? 0
self.pageControl.numberOfPages = numberOfImages
return(numberOfImages)
}