orange top-level property Null safety

Implementation

NBColor orange = const NBColor(
    0xfff97316,
    <String, Color>{
      'orange.50 ': Color(0xfffff7ed),
      'orange.100': Color(0xffffedd5),
      'orange.200': Color(0xfffed7aa),
      'orange.300': Color(0xfffdba74),
      'orange.400': Color(0xfffb923c),
      'orange.500': Color(0xfff97316),
      'orange.600': Color(0xffea580c),
      'orange.700': Color(0xffc2410c),
      'orange.800': Color(0xff9a3412),
      'orange.900': Color(0xff7c2d12),
    },
    'orange');