Examine source code of Countdown Timer Plus New

{
  "manifest_version": 2,
  "name": "Countdown Timer",
  "version": "1.0",
  "description": "Counts down to a specific date with additional useful features",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": false
  },
  "background": {
    "scripts": [
      "background.js"
    ],
    "persistent": false
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{3f2ab293-3919-4542-8cdc-3e24dd03331c}"
    }
  }
}