fix: handle object format for author field in package.json

[kaigritun]

Summary

Fixes #1334

Chrome extension manifest requires the author field to be a string, but npm's package.json allows author to be either:

• A string: "John Doe"
• An object: { "name": "John Doe", "email": "john@example.com", "url": "https://example.com" }

When the author field is an object, Plasmo was passing it directly to the manifest, causing the validation error:

Invalid Web Extension manifest
Expected type string

Changes

1. Added normalizeAuthor helper function in base.ts:

   • Returns undefined if no author is provided
   • Returns the string as-is if author is already a string
   • Converts object format to the standard npm string format: "Name <email> (url)"

2. Updated PackageJSON type in package-file.ts:

   • Added PackageAuthor type that accepts both string and object formats
   • Updated PackageJSON to use the new type for the author field

Example

package.json with object author:

{
  "author": {
    "name": "Gil B. Chan",
    "email": "bnbcmindnpass@gmail.com",
    "url": "https://github.com/jjangga0214"
  }
}

Generated manifest author:

{
  "author": "Gil B. Chan <bnbcmindnpass@gmail.com> (https://github.com/jjangga0214)"
}

References

• npm docs on people fields: https://docs.npmjs.com/cli/v11/configuring-npm/package-json#people-fields-author-contributors