Examine source code of Date Countdown

{
  "manifest_version": 2,
  "name": "Date Countdown",
  "version": "2.3.1.0",
  "description": "Count down to the dates that matter. Add events with a target date and time, watch the remaining days, hours and minutes tick live, and see days to the next one on the toolbar badge with a notification when it arrives.",
  "icons": {
    "32": "images/icon-32.png",
    "48": "images/icon-48.png",
    "64": "images/icon-64.png",
    "96": "images/icon-96.png",
    "128": "images/icon-128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{484ea9c0-6d89-4875-9963-37386a30bdea}",
      "strict_min_version": "101.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions": [
    "storage",
    "alarms",
    "notifications"
  ],
  "background": {
    "scripts": [
      "src/background.js"
    ]
  },
  "browser_action": {
    "default_title": "Date Countdown",
    "default_popup": "src/popup.html",
    "default_icon": {
      "32": "images/icon-32.png",
      "48": "images/icon-48.png",
      "64": "images/icon-64.png"
    }
  }
}