amber top-level property Null safety

Implementation

NBColor amber = const NBColor(
    0xfff59e0b,
    <String, Color>{
      'amber.50 ': Color(0xfffffbeb),
      'amber.100': Color(0xfffef3c7),
      'amber.200': Color(0xfffde68a),
      'amber.300': Color(0xfffcd34d),
      'amber.400': Color(0xfffbbf24),
      'amber.500': Color(0xfff59e0b),
      'amber.600': Color(0xffd97706),
      'amber.700': Color(0xffb45309),
      'amber.800': Color(0xff92400e),
      'amber.900': Color(0xff78350f),
    },
    'amber');