Allow comment introspection

[Pebkac03]

Allow comment introspection

I propose adding a property for comments to the Declaration class. I imagine it looking somethings like this:

/// This is the doc comment
final String someVar = 'some value';

void main() {
  // field = the declaration for someVar
  final FieldDeclaration field;
  print(field.comments.toString());
}

dart run
This is the doc comment
Exited.

Usecase

The usecase I have is creating a macro to generate a vscode json-schema file for a config service but I believe access to comments would be very useful in any kind of automatic file generation.

Resources

Implementation of similar functionality in code generation package dartgenerate: https://pub.dev/documentation/dartgenerate/latest/dartgenerate/FieldDeclaration-class.html.