fill method
Implementation
@override
OpSet fill(List<PointD> points) {
final OpSet set1 = fillPolygon(points, _config!, false);
final FillerConfig rotated =
_config!.copyWith(hachureAngle: _config!.hachureAngle! + 90);
final OpSet set2 = fillPolygon(points, rotated, false);
return OpSet(type: OpSetType.fillSketch, ops: set1.ops! + set2.ops!);
}