Examine source code of Alexa RANK

{
  "manifest_version": 2,
  "name": "Alexa RANK",
  "author": "VBS",
  "homepage_url": "https://www.thoduongluat.com",
  "version": "1.0.2",
  "description": "Alexa RANK Bar",
  "icons": {
    "48": "icons/extension.png"
  },
  "permissions": [
    "tabs",
    "webRequest",
    "<all_urls>",
    "storage"
  ],
  "page_action": {
    "browser_style": true,
    "default_icon": "icons/address-bar.png",
    "default_title": "Alexa rank",
    "default_popup": "popup/details.html"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "options_ui": {
    "page": "options/options.html",
    "browser_style": true
  }
}