Examine source code of Simple Dark Mode Toggle i

{
  "manifest_version": 2,
  "name": "Simple Dark Mode Toggle",
  "version": "1.0",
  "description": "Toggle dark mode on current page",
  "permissions": [
    "activeTab"
  ],
  "browser_action": {
    "default_icon": "icons/icon.png",
    "default_title": "Toggle Dark Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "applications": {
    "gecko": {
      "id": "darkmode-toggle-b4108c26@example.com"
    }
  }
}