lime top-level property Null safety

Implementation

NBColor lime = const NBColor(
    0xff84cc16,
    <String, Color>{
      'lime.50 ': Color(0xfff7fee7),
      'lime.100': Color(0xffecfccb),
      'lime.200': Color(0xffd9f99d),
      'lime.300': Color(0xffbef264),
      'lime.400': Color(0xffa3e635),
      'lime.500': Color(0xff84cc16),
      'lime.600': Color(0xff65a30d),
      'lime.700': Color(0xff4d7c0f),
      'lime.800': Color(0xff3f6212),
      'lime.900': Color(0xff365314),
    },
    'lime');