Coding Style Guidline.rst
Created a unified version of the Coding Style Guidelines
Extracted rules from various pandas website information as well as submission scripts that verify style requirements
Work in progress

- [x] closes #33851
- [ ] tests added / passed
- [ ] passes `black pandas`
- [ ] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [ ] whatsnew entry
