Examine source code of Important box icon

{
  "manifest_version": 2,
  "name": "Important box icon",
  "version": "1.0",
  "description": "The important box icon is often used to represent a container that is confidential, of high priority, or of special value.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_icon": "icon.png",
    "default_popup": "popup.html",
    "default_title": "Click me!"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{34006c5e-ffa2-4a44-8a68-0afb2a4e2540}"
    }
  }
}