Add keyword sort to pivot_table
- [x] closes #39143
- [x] tests added / passed
- [x] Ensure all linting tests pass, see [here](https://pandas.pydata.org/pandas-docs/dev/development/contributing.html#code-standards) for how to run them
- [x] whatsnew entry

This adds support for sort=False to pivot_table if we want to do this
thanks @phofl very nice! Will keyword sort be added to pivot? see #15105