Examine source code of Quick Dark Mode Toggle

{
  "manifest_version": 2,
  "name": "Quick Dark Mode Toggle",
  "version": "1.0",
  "description": "Toggle dark mode on the current page with one click.",
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Toggle Dark Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "tabs",
    "activeTab"
  ],
  "icons": {
    "48": "icons/icon.png"
  },
  "applications": {
    "gecko": {
      "id": "quick-dark-mode-toggle@example.com"
    }
  }
}