Examine source code of Joke Refresh Notification

{
  "name": "Joke Refresh Notification",
  "version": "1.0",
  "description": "Plays an audio clip saying 'Don't Close Your Browser On Me' on refresh. Based on a dream.",
  "permissions": [
    "webNavigation"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "manifest_version": 2
}