extensions/string_file_extension_ext library

1. fire_storage_impl package
2. documentation
3. extensions/string_file_extension_ext.dart

fire_storage_impl package

1. Libraries
2. constants/fire_storage_txt_const
3. data/data_sources/fire_storage_service_impl
4. data/data_sources/i_data_sources/i_fire_storage_service
5. extensions/file_name_generator
6. extensions/image_uploader
7. extensions/path_extensions
8. extensions/string_file_extension_ext
9. fire_storage_impl
10. typedefs/progress_callback
11. utils/content_type_util
12. utils/firebase_platform_exception_handler