fix: allow partial match for package title

[shuuji3]

🔗 Linked issue

fix #197

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 📰 Content (a new article or a change in the content folder)
• 🐞 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

Currently, we are using the default processTerm logic with prefix option in minisearch, which only allows the prefix-search for the title of the packages.

I modified the processing operation only for the title field of the package during search index construction so that the partial keyword in the middle of the package name can be searched.

I used the example code in the GitHub comment (lucaong/minisearch#194 (comment)) referred by the original issue #197.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.
  • N/A - this change does not affect the documentation.