Examine source code of Custom Notifications

{
  "description": "__MSG_extensionDescription__",
  "icons": {
    "512": "icons/icon64.png"
  },
  "version": "2.0",
  "manifest_version": 2,
  "name": "__MSG_extensionName__",
  "permissions": [
    "alarms",
    "notifications"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "strict_min_version": "121.0",
      "id": "{8a6ca5e3-9e02-4c68-ae52-fbbd37a209ed}"
    }
  }
}