Adds the current configuration of pycodestyle (as taken from the patchbot) to the src/tox.ini file. Thus, it can be run now locally via the cli pycodestyle. Moreover, tools like VS Code can pick it up automatically. The corresponding changes for the patchbot are done in sagemath/sage-patchbot#145.

Documentation will be added in #30361.

CC: @mkoeppe @fchapoton

Component: build

Author: Tobias Diez, Matthias Koeppe

Branch: 939e9e0

Reviewer: Matthias Koeppe, Tobias Diez

Issue created by migration from https://trac.sagemath.org/ticket/30408