How to get cell at center during scroll in UICollectionView

Issue #311

See Omnia https://github.com/onmyway133/Omnia/blob/master/Sources/iOS/UICollectionView.swift#L30

extension HorizontalUsersViewController: UIScrollViewDelegate {
    func scrollViewDidEndDecelerating(_ scrollView: UIScrollView) {
        let point = view.convert(collectionView.center, to: collectionView)

        guard
            let indexPath = collectionView.indexPathForItem(at: point),
            indexPath.item < users.count
        else {
            return
        }

        let user = users[indexPath.item]
        delegate?.didScrollTo(user)
    }
}