step method
Steps font weight thicker (positive) or lighter (negative) by step
clamped within FontWeight.w100 to FontWeight.w900.
Example:
FontWeight.w100.step(1)->FontWeight.w200FontWeight.w300.step(1)->FontWeight.w400FontWeight.w400.step(-1)->FontWeight.w300
Implementation
FontWeight step(int step) {
final newValue = (value + step * 100).clamp(100, 900);
return FontWeight.values[(newValue ~/ 100) - 1];
}