toJson method Null safety

Implementation

@override
Map<String, dynamic> toJson() {
  return {
    "fontFamily": fontFamily,
    "fontSize": fontSize,
    "fontWeight": fontWeight,
    "lineHeight": lineHeight,
    "letterSpacing": letterSpacing,
    "textAlign": textAlign,
    "fontStyle": fontStyle,
    "textTransform": textTransform,
    "textDecoration": textDecoration,
  };
}