Examine source code of Web Time Tracker

{
  "manifest_version": 2,
  "name": "Web Time Tracker",
  "version": "1.0",
  "description": "Track how much time you spend on each website today and this week.",
  "permissions": [
    "tabs",
    "storage",
    "idle"
  ],
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "48": "icon.png"
    }
  },
  "icons": {
    "48": "icon.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7192b2c5-79f4-4b49-bce4-e510ce9bc8b7}"
    }
  }
}