ENH: Add sort keyword to stack
- [x] xref #15105 (Replace xxxx with the GitHub issue number)
- [x] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [x] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added [type annotations](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#type-hints) to new arguments/methods/functions.
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

if the default were False (mentioned in the #15105), would it be straightforward to reproduce the current behavior with something like `df.stack(...).some_other_method()`?  If so, longer-term ideally we'd have users do that and not have a keyword Yeah that's a likely future behavior where we default to False and the deprecate this keyword, but we need to set it to true for backward compat Any other comments here @jbrockmendel? 