[ketpatil77]

Fixes #102.

Configure Flit to include tests/ and tox.ini in source distributions.

Validation on Windows / Python 3.11.9:

• Built the original archive and confirmed the reported test/configuration omission.
• Built corrected source and wheel distributions; verified 148 required test/configuration/fixture files match source bytes exactly. Installation wheels exclude tests/.
• Extracted-package suite after installing the declared deprecation-alias test dependency: 190 passed, 43 skipped, 2 failed. Both failures are help-output snapshots and reproduce on the source checkout with unchanged runtime/tests. The full suite is not claimed green. Mypy-specific tests, lint, and the Click/Python matrix were not validated.
• git diff --check passes.

This changes archive contents only; runtime code and test expectations are unchanged.