LDtk parser for Dart programming language

How to update:

1. Copy the contents of LDtk json schema and paste to quicktype
2. Quicktype settings:
   • Source type = JSON Schema,
   • Language = Dart,
   • Check 'Null Safety'
   • Check 'Put encoder & decoder in Class'
3. In the generated dart code, find all !, and replace with ,
4. Find json["cachedPixelData"]! and replace with json["cachedPixelData"] ?? <String, dynamic>{}