add pdbpp

[lauritowal]

"This module is an extension of the pdb module of the standard library. It is meant to be fully compatible with its predecessor, yet it introduces a number of new features to make your debugging experience as nice as possible." The "sticky" feature is quite useful for example https://pypi.org/project/pdbpp/

[CLAassistant]

All committers have signed the CLA.

[norabelrose]

Hmm maybe this is good but I've never tried it and strictly speaking it's not a dev dependency. The other dev dependencies are needed for the tests to run, or are for pre-commit stuff

[lauritowal]

alright, I'll close it then. The module is still worth a try :)