Examine source code of Key Click Sound FX

{
  "manifest_version": 2,
  "name": "Key Click Sound FX",
  "version": "1.0",
  "description": "Subtle mechanical keyboard click sound on key press. Auto-disabled for password fields.",
  "permissions": [
    "storage"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_start"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "key-click-sound-fx@amo",
      "strict_min_version": "140.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "icons": {
    "128": "icon.png"
  }
}