Examine source code of Tab Age Timer

{
  "manifest_version": 2,
  "name": "Tab Age Timer",
  "version": "1.0.1",
  "description": "Shows how long each tab has been open, counting up in the tab title.",
  "author": "Cygnus X Enterprises LLC",
  "homepage_url": "https://cygnusx.com",
  "permissions": [
    "tabs",
    "storage"
  ],
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_action": {
    "default_title": "Tab Age Timer"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{46e6c441-59f6-40fe-8ebd-98792387f053}"
    }
  }
}