docs: add Korean README

[hyeokjun32]

Summary

• Added README.ko.md for Korean readers.
• Kept README.md as the default English entry point.
• Added language links between English and Korean README files.

Validation

• bash scripts/smoke_default.sh: success
• python3 tests/test_manifest_compare_identity.py: 3 tests passed after rerun with permissions for results/latest.json write access

Impact

• Improves readability for Korean recruiters/interviewers.
• Keeps the public GitHub entry point English-first.
• Avoids the maintenance cost of translating every documentation file.

Notes

• Full docs remain English-first.
• Korean documentation is limited to README.ko.md for maintainability.
• Existing untracked build-ort/ and examples/model.onnx were not touched or committed.