payments/payment library

1. pagseguro_smart_flutter package
2. documentation
3. payments/payment.dart

pagseguro_smart_flutter package

1. Libraries
2. nfc_smart_flutter
3. pagseguro_smart_flutter
4. payments/handler/nfc_handler
5. payments/handler/payment_handler
6. payments/nfc
7. payments/payment
8. payments/utils/payment_types