Examine source code of Countdown Timer

{
  "manifest_version": 2,
  "name": "Countdown Timer",
  "version": "2.1.1",
  "description": "Counts down until a specified date and time",
  "icons": {
    "30": "icons/countdown30.png",
    "48": "icons/countdown.png"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_action": {
    "default_icon": "icons/countdown.png",
    "default_title": "Countdown",
    "default_popup": "popup/popup.html"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{e84d1aea-fbb4-4efb-8ebd-3f733f50128b}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}