Examine source code of Day/Night Theme Toggle

{
  "manifest_version": 2,
  "name": "Day/Night Theme Toggle",
  "version": "1.0",
  "description": "Easily switch between day and night themes on webpages.",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/theme-toggle-48.png",
    "default_popup": "popup.html",
    "default_title": "Theme Toggle"
  },
  "icons": {
    "48": "icons/theme-toggle-48.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{9f39411d-05fe-4dc7-b0eb-36fad40a388a}"
    }
  }
}