Completely rework the capitalization check algo in 'validate_rst_title_capitalization.py'
- [ ] Modify file scripts/validate_rst_title_capitalization
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

PR on rework of the script 'validate_rst_title_capitalization.py' to better handle the capitalization, the capitalization exceptions, with the use of exceptions in the form of tuples to allow different writings for a particular word. The idea is to be able to use two different types inside 'CAPITALIZATION_EXCEPTIONS': one-word string, or tuple containing a number of word elements, with different capitalization.
You can experiment it by replacing some exceptions inside 'CAPITALIZATION_EXCEPTIONS' by tuples containing several times the same exception with different capitalisations. I already did it for 'categorical' with ('categorical', 'Categorical')