Examine source code of WebsiteIP

{
  "name": "WebsiteIP",
  "description": "Display the IP(s) of the current tab URL",
  "version": "1.2.3",
  "manifest_version": 2,
  "homepage_url": "https://github.com/floreo/WebsiteIP",
  "permissions": [
    "activeTab",
    "dns"
  ],
  "icons": {
    "64": "icons/dark-icon.png"
  },
  "browser_action": {
    "theme_icons": [
      {
        "dark": "icons/dark-icon.png",
        "light": "icons/light-icon.png",
        "size": 64
      }
    ],
    "browser_style": true,
    "default_title": "WebsiteIP",
    "default_popup": "popup/websiteip.html"
  }
}