[ketpatil77]

Source distributions omit tox.ini, so downstream packagers cannot discover or run the project's test environments. Adding only that file also leaves its referenced requirements and coverage configuration missing.

Include tox.ini, dev-requirements.txt, .coveragerc, and docs/source/requirements.txt in the source archive, with an unreleased changelog entry. This preserves the existing tox environments and coverage threshold.

Fixes #129.

Validation on Windows / Python 3.11.9:

• Built the original sdist and confirmed all four files are absent.
• Built the corrected sdist and checked all four archived files match the source bytes.
• Installed the package and test dependencies from the extracted archive.
• Ran the normal test command from that extracted archive: 2,914 passed, 100% coverage.
• git diff --check passes.

AI-assisted contribution; the archive checks and test results above were run locally. Other Python versions, docs builds, and type checks were not run.