Introduces sorting capabilities within the Redner substitution

Note that we implemented sorting functionality and added unit tests.

The changes include:

- Creation of a new utility file `utils/sorting.py` implementing sorting
functionalities such as :
`find_field_with_sort_order`,
`parse_fields_with_sort_directions`, and `sortkey`.
- Addition of a new file `tests/test_sorting.py` containing unit tests for
sorting logic.