Examine source code of Scroll Sound

{
  "manifest_version": 2,
  "name": "Scroll Sound",
  "version": "1.0",
  "description": "Plays a short paper-rustle or custom sound when the user scrolls the page.",
  "permissions": [
    "storage",
    "activeTab"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{948a547e-0e6a-4d70-8c1a-a23fae397440}"
    }
  }
}