Examine source code of Time Tracker for Websites

{
  "manifest_version": 2,
  "name": "Time Tracker for Websites",
  "version": "1.0",
  "description": "Display a timer in the tab to show how much time you've spent on a specific website.",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_popup": "popup.html"
  },
  "icons": {
    "48": "icons/icon48.png",
    "96": "icons/icon96.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{82a2cb5e-9973-4cc0-baa3-9db99de6c2c8}"
    }
  }
}