ci: skip CI on docs-only changes via paths-ignore

[martinkersner]

Summary

Adds a paths-ignore filter to the push trigger in .github/workflows/python-package.yml so pushes that touch only docs/markdown/LICENSE/.gitignore skip the workflow. Any change to code, tests, requirements, or the workflow file itself still runs the full 5-version matrix (3.10–3.14).

on:
  push:
    paths-ignore:
      - '**.md'
      - 'docs/**'
      - 'LICENSE'
      - '.gitignore'

The build job, matrix, and all steps are unchanged — only the trigger block was modified.

Rationale: paths-ignore (blocklist) vs paths (allowlist)

paths-ignore fails safe: any new or unanticipated code path still triggers CI. A paths allowlist would silently skip CI for any path someone forgot to add. The ignore list is deliberately limited to files that genuinely cannot affect the lint checks (black/flake8 only run on .py): markdown, the docs/** tree (verified: only .md/css/images, no Python), LICENSE, and .gitignore.

Branch protection

main has no branch protection (verified: repos/Bisonai/datamaxi-python/branches/main/protection → 404), so a skipped workflow leaves no required-check pending. No no-op fallback job is needed; a plain paths-ignore filter is sufficient.

Test / validation plan

• YAML validated with yaml.safe_load (parses OK).
• Diff confirmed scoped: only the on: trigger block changed; job/matrix/steps untouched.
• To confirm behavior after merge: a docs-only push (e.g. editing README.md) should not trigger python-package.yml; a push touching any .py/requirements/workflow file should still run the full matrix.

Closes #104