commands/print_builder library

1. flutter_thermal_printer_plus package
2. documentation
3. commands/print_builder.dart

flutter_thermal_printer_plus package

1. Libraries
2. commands/esc_pos_commands
3. commands/image_processor
4. commands/print_builder
5. flutter_thermal_printer_plus
6. flutter_thermal_printer_plus_method_channel
7. flutter_thermal_printer_plus_platform_interface
8. models/paper_size
9. models/printer_info
10. platform/thermal_printer_platform