docs: refine function usages

[NozomuIkuta]

🔗 Linked issue

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Resolves #664

As @Barbapapazes suggested, I replace eventHandler calls with defineEventHandler because the latter is more used.
At the same time, I also fixed the following points:

• Sort imports in alphabetical order
  • In this point, it is better to fix docs(examples/from-expressjs-to-h3): add node middleware usage #663 for consistency
• Fix typos
  • Typo fixed by docs: fix import example in 4.event.md #658 is included in this PR too (so, it should be merged first)
• Refine sample codes

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[cloudflare-pages]

Deploying with    Cloudflare Pages

Latest commit:	43854af
Status:	✅  Deploy successful!
Preview URL:	https://0c25bdc3.unjs-h3.pages.dev
Branch Preview URL:	https://docs-refine-function-usages.unjs-h3.pages.dev

View logs

[pi0]

Thanks ❤️