toJson method Null safety

Implementation

Map<String, dynamic> toJson() {
  return {
    "fontSize": fontSize,
    "letterSpacing": letterSpacing,
    "fontWeight": fontWeight,
    "lineHeight": lineHeight,
    "component": component,
    "spaces": spaces,
    "sizes": sizes,
    "borders": borders,
    "radii": radiuses,
    "colors": color,
    "shadows": shadows
  };
}