Examine source code of Server IP

{
  "manifest_version": 2,
  "name": "Server IP",
  "version": "2.1",
  "description": "Displays website servers IP address and the reverse DNS of that IP address.",
  "icons": {
    "48": "icons/ip.svg",
    "96": "icons/ip.svg"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "dns",
    "<all_urls>",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "ip.js"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "server_ip@1x.dk",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}