trueGray top-level property Null safety

Implementation

NBColor trueGray = const NBColor(
    0xff737373,
    <String, Color>{
      'trueGray.50 ': Color(0xfffafafa),
      'trueGray.100': Color(0xfff5f5f5),
      'trueGray.200': Color(0xffe5e5e5),
      'trueGray.300': Color(0xffd4d4d4),
      'trueGray.400': Color(0xffa3a3a3),
      'trueGray.500': Color(0xff737373),
      'trueGray.600': Color(0xff525252),
      'trueGray.700': Color(0xff404040),
      'trueGray.800': Color(0xff262626),
      'trueGray.900': Color(0xff171717),
    },
    'trueGray');