需要齐鲤，tabbar頂部無橫線斥废，不帶模糊和透明度效果，遇到小坑给郊，特此記錄,
appearance 和 unselectedItemTintColor 不可兼得牡肉，只能取其一。
tabBarController.tabBar.tintColor = UIColor.white
tabBarController.tabBar.unselectedItemTintColor = UIColor.white.withAlphaComponent(0.5)
tabBarController.tabBar.barTintColor = #colorLiteral(red: 0.6392156863, green: 0.6862745098, blue: 0.8, alpha: 1)
tabBarController.tabBar.shadowImage = UIImage()
tabBarController.tabBar.backgroundImage = UIImage(named: "tabbarBg")
// if #available(iOS 13, *) {
// let appearance = tabBarController.tabBar.standardAppearance.copy();
// appearance.backgroundColor = #colorLiteral(red: 0.6392156863, green: 0.6862745098, blue: 0.8, alpha: 1)
// appearance.shadowImage = UIImage(named: "alpha");
// appearance.configureWithTransparentBackground();
// tabBarController.tabBar.standardAppearance = appearance;
// } else {
// tabBarController.tabBar.backgroundImage = UIImage();
// tabBarController.tabBar.shadowImage = UIImage();
// }
