fix: Enable umlaut characters for prompts

[DevFreeze]

Description

When using mason_logger's prompt function with an umlaut, the character is not displayed correctly.

Steps To Reproduce

Create a new Dart app with dart create. Add mason_logger as a dependency and replace bin\project_name.dart with:

import 'package:mason_logger/mason_logger.dart';

void main(List<String> arguments) {
  final logger = Logger();
  final name = logger.prompt('What is your name?');
  print('Hello, $name!');
}

Expected Behavior

When entering a name with an Umlaut, e.g.: John Dö, then the output should also display the umlaut correctly.

Observed Behavior

$ dart run .\mason_logger_repro.dart my_command
What is your name? John Dö
Hello, John Dö!