fix(types): more accurately represent ParsedContentMeta

[harlan-zw]

🔗 Linked issue

❓ 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

• _slug is not used but is in the types, which is misleading
• full list of id types (_type, _file, _extension) are missing
• added types to the path-meta file to ensure stricter type adherence

📝 Checklist

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

[netlify]

‼️ Deploy request for nuxt-content rejected.

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🔨 Latest commit	1591b6c