docs: fix spelling and grammar mistakes in Event Object

[dgxo]

❓ 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

Various spelling and grammar mistakes in the (Event Object)[https://h3.unjs.io/guide/event] documentation page.

📝 Checklist

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

[nozomuikuta]

Thank you!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.72%. Comparing base (a58d7c9) to head (3936a34).
Report is 62 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #738      +/-   ##
==========================================
+ Coverage   77.83%   79.72%   +1.88%     
==========================================
  Files          47       53       +6     
  Lines        4286     5297    +1011     
  Branches      611      674      +63     
==========================================
+ Hits         3336     4223     +887     
- Misses        933     1056     +123     
- Partials       17       18       +1     

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