docs(routing): add middleware section

[Barbapapazes]

🔗 Linked issue

fix #1306

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 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)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Usage of middlewares are not documented. This PR is a try to add documentation about middlewares.

📝 Checklist

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

[nuxt-studio]

✅ Live Preview ready!

Name	Edit	Preview	Latest Commit
nitro	Edit on Studio ↗︎	View Live Preview	06b7ddc

[Hebilicious]

This is looking good, thanks @Barbapapazes !

[codecov]

Codecov Report

Merging #1307 (5558a13) into main (1d0c120) will not change coverage.
Report is 63 commits behind head on main.
The diff coverage is n/a.

❗ Current head 5558a13 differs from pull request most recent head 06b7ddc. Consider uploading reports for the commit 06b7ddc to get more accurate results

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  Files          71       71           
  Lines        7241     7241           
  Branches      723      723           
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  Hits         5550     5550           
  Misses       1690     1690           
  Partials        1        1           

[pi0]

Thanks! For now added it under routing section for similification