widgets/snackbar_container library

1. snackbarx package
2. documentation
3. widgets/snackbar_container.dart

snackbarx package

1. Libraries
2. models/snackbar_config
3. models/snackbar_type
4. snackbar_x_manager
5. snackbarx
6. widgets/base_snackbar
7. widgets/snackbar_container