migrate to null safety [2.0.0] - 27-Mar-2021 [1.0.5] - 27-Dec-2019 change image of demo [1.0.4] - 27-Dec-2019 fix bug DigitToWord and add new feature add DigitFormat add DigitInputFormat [1.0.3] - 23-Dec-2019 fix image demo issues [1.0.2] - 23-Dec-2019 add image of demo [1.0.1] - 23-Dec-2019 fix link in README.md [1.0.0] - 23-Dec-2019 fix analysis issues [0.0.1] - 23-Dec-2019 changing digit to the Persian word