Examine source code of downloadCambridgeAudio

{
  "manifest_version": 2,
  "name": "downloadCambridgeAudio",
  "version": "1.2",
  "description": "used to download Mp3 Audio From Dictionary Cambridge Page",
  "permissions": [
    "notifications"
  ],
  "background": {
    "scripts": [
      "background-script.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "*://dictionary.cambridge.org/*"
      ],
      "js": [
        "content-script.js"
      ]
    }
  ],
  "default_locale": "en"
}