Examine source code of Show External IP 2.0

{
  "manifest_version": 2,
  "name": "Show External IP",
  "description": "Detects and shows your current external IP address, Location and Timezone (as seen by http://ip-api.com/json/) in a convenient popup.",
  "version": "1.0.6",
  "icons": {
    "16": "icon-dark.svg",
    "48": "icon-dark.svg",
    "128": "icon-dark.svg"
  },
  "browser_action": {
    "default_icon": "icon-dark.svg",
    "default_popup": "showextip.html",
    "default_title": "Show External IP",
    "theme_icons": [
      {
        "light": "icon-light.svg",
        "dark": "icon-dark.svg",
        "size": 32
      }
    ]
  },
  "permissions": [
    "http://ip-api.com/json/",
    "clipboardWrite"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{40979467-1f3f-44ef-96c8-3efcdda7ab19}"
    }
  }
}