helpers/extensions/null_extension library

1. pagify package
2. documentation
3. helpers/extensions/null_extension.dart

pagify package

1. Libraries
2. generated/assets
3. helpers/add_frame
4. helpers/custom_bool
5. helpers/data_and_pagination_data
6. helpers/errors
7. helpers/extensions/null_extension
8. helpers/extensions/zero_extension
9. helpers/status_stream
10. pagify
11. widgets/pagination_helper_refresh_indicator
12. widgets/text