feat: add `initialize_in_field_declaration` rule

[ricardodalarme]

Description

Add the new initialize_in_field_declaration rule, introduced in Dart 3.13. Ref: https://dart.dev/tools/diagnostics/initialize_in_field_declaration

[unicoderbot]

Great, I will work on a PR and push it soon.

• Preparing environment
  • Cloning repository
  • Setting up dev environment
• Working on changes
• Reviewing changes
• Opening pull request

I've opened a pull request: #230