How to sync multiple CAAnimation

Issue #600

Use same CACurrentMediaTime

final class AnimationSyncer {
    static let now = CACurrentMediaTime()

    func makeAnimation() -> CABasicAnimation {
        let animation = CABasicAnimation(keyPath: "opacity")
        animation.fillMode = .forwards
        animation.fromValue = 0
        animation.toValue = 1
        animation.repeatCount = .infinity
        animation.duration = 2
        animation.beginTime = Self.now
        animation.autoreverses = true
        animation.timingFunction = CAMediaTimingFunction(name: .easeInEaseOut)
        return animation
    }
}