Examine source code of Beautiful Stopwatch

{
  "manifest_version": 2,
  "name": "Beautiful Stopwatch",
  "version": "1.0",
  "description": "A simple stopwatch extension with a beautiful UI",
  "permissions": [
    "activeTab"
  ],
  "icons": {
    "48": "icon.png"
  },
  "action": {
    "default_popup": "popup.html"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{404ce233-58a8-4c51-b65f-98a354ccbc84}"
    }
  }
}