package:json_serializable v6.13.1

• Improve error message when generating code for Record types with unsupported
  fields.
  (#1559)
• Require analyzer: '>=10.0.0 <13.0.0'
• Require build: ^4.0.4
• Require dart_style: ^3.1.4
• Require source_gen: ^4.1.2
• Require source_helper: ^1.3.10