Examine source code of Pension Calculator

{
  "manifest_version": 2,
  "name": "Pension Calculator",
  "version": "1.0",
  "description": "A simple pension savings calculator.",
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icons/icon.png"
  },
  "icons": {
    "48": "icons/icon.png"
  },
  "permissions": [],
  "browser_specific_settings": {
    "gecko": {
      "id": "{276ed6b4-5c6a-410a-a0ee-8b4f227b5c53}"
    }
  }
}