lerp method
Returns the tween value at the given animation value (alias for evaluate).
Example:
final tween = Tween(begin: 0.0, end: 100.0);
tween.lerp(0.5); // 50.0
Implementation
T lerp(double t) {
if (begin == null) return end as T;
if (end == null) return begin as T;
return (begin as dynamic).lerp(end as dynamic, t) as T;
}