Support for CustomViews in show() method?!

[amarildolucas]

Like UIActivityIndicatorView, it would be nice if DotsLoadingView could be added to any CustomView.

public func show() {
        if let rootViewController = UIApplication.shared.windows.first?.rootViewController {
            rootViewController.view.addSubview(self)
            self.center = rootViewController.view.center
            self.startAnimation()
        } else {
            print("Cannot show DotsLoadingView.")
        }
    }