easeInOutQuad constant
A cubic animation curve that starts slowly, speeds up, and then ends slowly. This curve can be imagined as Curves.easeInQuad as the first half, and Curves.easeOutQuad as the second.
Compared to Curves.easeInOutSine, this curve is slightly steeper.
Derived from Robert Penner’s easing functions.
Implementation
static const Cubic easeInOutQuad = Cubic(0.455, 0.03, 0.515, 0.955);