Examine source code of External link icon

{
  "manifest_version": 2,
  "name": "External link icon",
  "version": "1.0",
  "description": "External link icons are often used to let users know that when they click a link, they will be taken to another website (outside the current app or website).",
  "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": "{a863d213-31f3-4771-af6e-e45fc4aade9d}"
    }
  }
}