Examine source code of download-notify

{
  "manifest_version": 2,
  "name": "download-notify",
  "version": "1.1",
  "description": "Creates a notification for download events",
  "icons": {
    "48": "icons/icon-48.png"
  },
  "background": {
    "scripts": [
      "download-notify.js"
    ]
  },
  "permissions": [
    "downloads",
    "notifications"
  ]
}