Add UI chatbot performance comparison article

[foxhub2020]

Closes #9

Summary

• Adds a research-backed article comparing UI-based and text-only chatbots across task completion, time-on-task, and satisfaction.
• Focuses on a practical measurement framework and scorecard rather than a generic product pitch.
• Positions OpenUI naturally as the runtime path for structured generated interfaces.

Validation

• npx --yes markdownlint-cli2 "Articles/UI-Based Chatbots vs Text-Based Chatbots - A Performance Comparison Across Completion Time and Satisfaction.md"
• Link checks for cited OpenUI/Thesys/NNG/GitHub references returned 200 where HEAD requests were accepted. ScienceDirect returned 403 to HEAD but the PII article URL is included as a citation target.