package:code_builder v4.5.0

• Require Dart 2.19
• Add support for emitting type parameters for typedefs.
• Add support for class modifiers.
• Add support for records (both types and record literals).
• Add literalSpread and literalNullSafeSpread to support adding spreads to
  literalMap.

void main() {
  // Creates a map
  // {
  //   ...one,
  //   2: two,
  //   ...?three,
  // }
  final map = literalMap({
    literalSpread(): refer('one'),
    2: refer('two'),
    literalNullSafeSpread(): refer('three'),
  });
}