Add IPython integration

[darshan-Jahagirdar]

Fixes #10.

IssueHunt: https://oss.issuehunt.io/r/Qix-/better-exceptions/issues/10

Summary:

• Add an IPython integration module that patches IPython's showtraceback hook.
• Expose the integration as an IPython extension via %load_ext better_exceptions.integrations.ipython.
• Preserve IPython's original traceback handling for syntax errors and special traceback modes.
• Document IPython usage in the README.

Notes:

• AI-assisted with OpenAI Codex; I reviewed the implementation and tests.

Verification:

• PYTHONPATH=. python test/test_ipython.py
• PYTHONPATH=. python test/test_logging.py
• python -m py_compile better_exceptions/integrations/ipython.py test/test_ipython.py
• Real IPython 9.13.0 extension smoke test with InteractiveShell.instance()
• git diff --check

[darshan-Jahagirdar]

Validation update for this PR:

py -3.11 -B test\test_ipython.py
git diff --check

Result: both passed.

Notes: I used Python 3.11 because Python 3.14 no longer includes distutils, which this older package still imports in setup.py. On Windows the package imports colorama, so I installed colorama into a temporary test-only directory via pip --target, added that directory to PYTHONPATH, ran the test, and removed the temp directory afterward.