Examine source code of Web Time Tracker

{
  "manifest_version": 2,
  "name": "Web Time Tracker",
  "version": "1.0.0",
  "description": "Tracks how much time you spend on websites and shows a searchable breakdown.",
  "permissions": [
    "tabs",
    "storage",
    "idle",
    "notifications",
    "<all_urls>"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": true
  },
  "browser_action": {
    "default_title": "Web Time Tracker",
    "default_popup": "popup.html"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3f0c9a5d-1be4-4ee1-9a7b-bf77f2c3d41e}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}