lerp method
lerp
return a value between begin
and end
Implementation
@override
Rect lerp(double t) => Rect.fromLTRB(
lerpNNDouble(begin.left, end.left, t),
lerpNNDouble(begin.top, end.top, t),
lerpNNDouble(begin.right, end.right, t),
lerpNNDouble(begin.bottom, end.bottom, t),
);