Examine source code of TimerPro

{
  "manifest_version": 2,
  "name": "TimerPro",
  "version": "1.0",
  "description": "TimerPro is an extension for alarms, timers, and stopwatch in your browser.",
  "icons": {
    "48": "icon.png"
  },
  "browser_action": {
    "default_popup": "popup.html",
    "default_icon": "icon.png"
  },
  "permissions": [
    "storage"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{3cd0c2d0-fb8e-4ddc-bcba-a7bf2dd26d9f}"
    }
  }
}