Examine source code of latest-download

{
  "description": "Shows the last downloaded item, and lets you open or delete it",
  "manifest_version": 2,
  "name": "latest-download",
  "version": "3.0",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/latest-download",
  "icons": {
    "48": "icons/page-48.png"
  },
  "permissions": [
    "downloads",
    "downloads.open"
  ],
  "browser_action": {
    "browser_style": true,
    "default_icon": "icons/page-32.png",
    "default_title": "Latest download",
    "default_popup": "popup/latest_download.html"
  }
}