Examine source code of Countdown Calendar

{
  "manifest_version": 2,
  "name": "Countdown Calendar",
  "version": "0.0.0.1",
  "description": "Year calendar with the ability to mark dates to countdown to/from, and set a primary countdown for the icon badge.",
  "author": "pinegala@gmail.com",
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icon16.png",
      "48": "icon48.png",
      "128": "icon128.png"
    },
    "default_title": "Countdown Calendar"
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "icons": {
    "16": "icon16.png",
    "48": "icon48.png",
    "128": "icon128.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{670a9d7c-d3b8-4507-bdd8-432c18418dbd}"
    }
  }
}