lighten function
Implementation
Color lighten(Color color, {double amount = 0.5}) {
assert(amount >= 0 && amount <= 1, 'Amount must be between 0 and 1');
final hsl = HSLColor.fromColor(color);
final hslLight = hsl.withLightness((hsl.lightness + amount).clamp(0.0, 1.0));
return hslLight.toColor();
}