[DOC]: Add warning about rolling sums with large values
- [x] closes #11645 
- [x] closes #28244 (probably closes that one too)
- [x] passes `black pandas`
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`

Added a warning within the user guide.

thanks @phofl very nice! keep em coming!