Examine source code of macOS Dictionary Lookup

{
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "description": "__MSG_extensionDescription__",
  "version": "1.3.3",
  "permissions": [
    "contextMenus"
  ],
  "background": {
    "scripts": [
      "lookup.js"
    ]
  },
  "icons": {
    "16": "book.svg",
    "24": "book.svg",
    "32": "book.svg",
    "48": "book.svg",
    "64": "book.svg",
    "96": "book.svg",
    "128": "book.svg"
  },
  "default_locale": "en"
}