pre-/post- processing is not tested

Currently the pre-/post- processing functions are not tested

First testing shows that `get_config_dict` will also have to be adjusted, otherwise 'test_compare_config' will fail due to differing value caused by pre-/post- processing

[tests/base_test_setup.py](https://github.com/pidi3000/Badger_Config_Handler/blob/main/tests/base_test_setup.py)