[FR]: Add support for a custom settings file

[ricardodalarme]

Is there an existing issue for this?

• [X] I have searched the existing issues

Describe the problem

I'd like to configure the package in a specific file instead of the pubspec, because I like to keep the settings well-documented to help the team. Example:

Describe the solution

Make the package also accept settings from a flutter_gen.yaml file

Additional context

No response

Code of Conduct

• [X] I agree to follow this project's Code of Conduct