Add comments to see translation in IDE

[vanlooverenkoen]

Original ticket: icapps/flutter-icapps-translations#31

@ikbendewilliam
I18n adds the default translation in file as description, this has the effect that in your IDE you can immediately see what it means and prevents wrong labels.

  /// No description provided for @careerInfoTitle.
  ///
  /// In en, this message translates to:
  /// **'Info'**
  String get careerInfoTitle;