Change user interface style by inverting it

AppDelegate+UserInterfaceStyle.swift

import UIKit

extension AppDelegate {
    func changeUserInterfaceStyle() {
        guard let window = window else { return }

        if window.overrideUserInterfaceStyle == .unspecified {
            window.overrideUserInterfaceStyle = UIScreen.main.traitCollection.userInterfaceStyle == .light ? .dark : .light
        } else {
            window.overrideUserInterfaceStyle = window.overrideUserInterfaceStyle == .light ? .dark : .light
        }
    }
}