buddhist_datetime_dateformat_sns 1.0.7

fork of https://github.com/teerasej/dart-flutter-buddhist-datetime-dateformat to support sound null safety

1.0.6 05/06/2020.

• fix link to Thai manual, finally

1.0.5 05/06/2020.

• fix link to Thai manual

1.0.4 05/06/2020.

• Add example photo in README.md

1.0.3 05/06/2020.

• fix miscalculation in DateFormat

1.0.2 05/06/2020.

• Add "How to use"
• Add "How to use" in Thai

1.0.1 05/06/2020.

• Formatted code
• add example

1.0.0 05/06/2020.

• Add extension for DateFormat with Thai's Buddhist calendar support (ค.ศ. เป็น พ.ศ.).
• Add extension for DateTime that can get year by converted into Buddhist calendar's value.