Examine source code of Custom Alert Tones

{
  "description": "__MSG_extensionDescription__",
  "icons": {
    "64": "icons/icon.png"
  },
  "version": "2.0",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "permissions": [
    "alarms",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "91.1.0",
      "id": "{9c7b6393-1973-4c60-ba89-e9597a28b9a6}"
    }
  }
}