Examine source code of Douban Book+

{
  "name": "Douban Book+",
  "description": "Only 1-click from Douban to your favorite ebook platforms",
  "version": "1.5.1",
  "manifest_version": 2,
  "homepage_url": "https://doubanbook.plus/",
  "icons": {
    "16": "logo/icon16.png",
    "32": "logo/icon32.png",
    "128": "logo/icon128.png"
  },
  "browser_action": {
    "default_icon": "logo/icon128.png",
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage",
    "https://api.old-panda.com/GetEBookUrls"
  ],
  "background": {
    "page": "background-page.html",
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "*://book.douban.com/subject/*"
      ],
      "js": [
        "content.js"
      ]
    }
  ],
  "web_accessible_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/no-book.png"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{622287fe-ef8a-43ac-a6bc-c9b860766407}"
    }
  }
}