Examine source code of Save Electricity Timer

{
  "manifest_version": 2,
  "name": "Save Electricity Timer",
  "version": "1.0",
  "description": "Reminds you to shut down your computer after a period of inactivity.",
  "permissions": [
    "idle",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9e688297-ca21-4985-8cce-b6fa1151552f}"
    }
  }
}