utils/date_time library

1. flight_ticket_booking_card package
2. documentation
3. utils/date_time.dart

flight_ticket_booking_card package

1. Libraries
2. data/models/flight_info
3. flight_ticket_booking_card
4. main
5. utils/date_time
6. utils/flight_time_calculator
7. widget/barcode_painter
8. widget/cut_separator
9. widget/ticket_card
10. widget/ticket_clipper
11. widget/ticket_painter
12. widget/ticket_shape