Examine source code of Douban Book+

{
  "name": "Douban Book+",
  "description": "Only 1-click from Douban to your favorite ebook platforms",
  "version": "1.6.0",
  "manifest_version": 3,
  "homepage_url": "https://doubanbook.plus/",
  "browser_specific_settings": {
    "gecko": {
      "id": "{622287fe-ef8a-43ac-a6bc-c9b860766407}",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ],
        "optional": []
      }
    },
    "gecko_android": {
      "strict_min_version": "142.0"
    }
  },
  "icons": {
    "16": "logo/icon16.png",
    "32": "logo/icon32.png",
    "128": "logo/icon128.png"
  },
  "action": {
    "default_icon": "logo/icon128.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "https://api.old-panda.com/GetEBookUrls"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "type": "module"
  },
  "content_scripts": [
    {
      "matches": [
        "*://book.douban.com/subject/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_resources": [
    {
      "resources": [
        "img/weread-logo.png",
        "img/duokan-logo.png",
        "img/kindle-logo.png",
        "img/ireader-logo.png",
        "img/snail-logo.png",
        "img/douban-logo.svg",
        "img/dedao-logo.png",
        "img/zlibrary-logo.png",
        "img/anna-logo.svg",
        "img/dangdang-logo.png",
        "img/jd-logo.svg",
        "img/no-book.png"
      ],
      "matches": [
        "<all_urls>"
      ]
    }
  ]
}