This pull request mainly updates the README.md to improve formatting and clarity, and adds a new documentation file for the opening-quiz skill. The most notable changes include switching from asterisks to underscores for contributor attribution, adding code examples for using Claude Skills, and introducing a comprehensive skill guide for opening quizzes.

New Usage Instructions

• Added step-by-step code examples in the "Using Skills in Claude Code" section to show how to install and run skills, improving onboarding for new users.

New Skill Documentation

• Added opening-quiz/SKILL.md with detailed instructions, examples, and a JSON template for the new opening-quiz skill, including usage tips and common use cases.

Skill List Update

• Added the opening-quiz skill to the list of development & code tools in the README.md, with a brief description and contributor attribution.