Align .speed modifier for Cocoa animations with SwiftUI

[maximkrouk]

• Align with SwiftUI animations

  A quote from SUI docs:

  • Setting the speed of an animation changes the duration of the animation by a factor of speed. A higher speed value causes a faster animation sequence due to a shorter duration. For example, a one-second animation with a speed of 2.0 completes in half the time (half a second).
  • Setting speed to a lower number slows the animation, extending its duration. For example, a one-second animation with a speed of 0.25 takes four seconds to complete.

• Add issue reporting
  Since the behaviour is inverted now there is a chance of division by zero

[stephencelis]

Good catches, thanks!