Examine source code of FollowUp

{
  "manifest_version": 2,
  "name": "FollowUp",
  "version": "1.1",
  "description": "automatic update the bookmarks to the current page",
  "permissions": [
    "bookmarks",
    "tabs",
    "notifications"
  ],
  "background": {
    "scripts": [
      "followUp.js"
    ]
  }
}