Add Aho–Corasick multi-pattern automaton

[f-gueguen]

Summary

• Implement Aho–Corasick automaton with case sensitivity option
• Expose createAhoCorasick in index and docs; extend search example
• Add unit tests for overlapping/case-insensitive/empty patterns
• Mark roadmap entry and update docs list

Testing

• npm run lint
• npm run typecheck
• npm test
• npm run build