Examine source code of Calculator JX

{
  "manifest_version": 2,
  "name": "Calculator",
  "version": "1.0",
  "description": "Standard calculator",
  "icons": {
    "48": "icons/calculator icon.png"
  },
  "browser_action": {
    "default_icon": "icons/calculator icon.png",
    "default_title": "Standard calculator",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "activeTab",
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{87A59787-CD8E-43A4-B2C6-FEA49B850518}"
    }
  }
}