Examine source code of Simple Calculator Live

{
  "manifest_version": 2,
  "name": "Simple Calculator",
  "version": "1.0",
  "description": "A basic calculator extension",
  "browser_action": {
    "default_popup": "popup.html",
    "default_title": "Calculator"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{5f59563c-b013-4444-af6b-ecebbf1e9cce}"
    }
  }
}