docs: adoption content — comparison writeup and examples

[krkarma777]

• Short "why another diff library" writeup expanding the README benchmark section: exact-by-default + heuristic escape hatch + worst-case numbers, with reproducible methodology (`npm run bench`).
• Runnable examples: StackBlitz/CodeSandbox links in the README quick start.
• Post to relevant communities once written (r/javascript, Korean dev communities) — downloads are currently ~all mirror/scanner traffic, so real-user adoption needs visibility work.