Parameterized JsonConverter

I would like to request that JsonConverter classes support parameter.

Given this Example:

```dart
class UserProfile {

@DateTimeLocalJsonConverter()
final DateTime? birthdate;

const UserProfile(this.birthdate);
}
```

```dart
class DateTimeUtcJsonConverter extends JsonConverter {
/// if true, utc to local conversion is disabled
final bool disableFromUtc;

/// if true, local to utc conversion is disabled
final bool disableToUtc;

const DateTimeUtcJsonConverter({this.disableFromUtc = false, this.disableToUtc = false});

@override
DateTime fromJson(String json) {
if (disableFromUtc) return DateTime.parse(json);

return DateTime.parse(json).toLocal();
}

@override
String toJson(DateTime object) {
if (disableToUtc) return object.toIso8601String();

return object.toUtc().toIso8601String();
}
}

```

As we see in the example, it was a bad idea to convert the birthday of a user into a utc date.
If the code generator would support parameter in JsonConverter, this would be helpful in reversing this mistake.

The alternative for parameter are currently writing a complete converter with the correct conversion or using a typedef.
```dart
const localDateTimeConverter = DateTimeUtcJsonConverter(disableToUtc: true);
```