fix: Enable umlaut characters for prompts

**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 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!