Examine source code of Audio Downloader

{
  "manifest_version": 2,
  "name": "Audio Downloader",
  "version": "1.0",
  "description": "Manually track and download audio files by entering their URLs.",
  "background": {
    "scripts": [
      "popup.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "activeTab"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{1468f476-200d-4284-9dd3-8f5ca328d740}"
    }
  }
}