Examine source code of DeskTime url fetcher

{
  "manifest_version": 2,
  "name": "DeskTime url fetcher",
  "version": "4.1.1",
  "description": "This extension allows DeskTime client to read current url.",
  "homepage_url": "https://desktime.com",
  "applications": {
    "gecko": {
      "strict_min_version": "80.0"
    }
  },
  "icons": {
    "48": "icons/online-48.svg",
    "96": "icons/online-96.svg"
  },
  "permissions": [
    "tabs"
  ],
  "browser_action": {
    "default_title": "DeskTime",
    "default_icon": "icons/online-96.svg",
    "browser_style": true
  },
  "background": {
    "scripts": [
      "fetcher.js"
    ]
  }
}