Examine source code of Simple Dark Mode Toggle

{
  "manifest_version": 2,
  "name": "Simple Dark Mode Toggle",
  "version": "1.0",
  "description": "Toggle dark mode on/off for any page.",
  "permissions": [
    "tabs",
    "<all_urls>"
  ],
  "browser_action": {
    "default_icon": {
      "48": "icons/icon-48.png",
      "96": "icons/icon-96.png"
    },
    "default_title": "Toggle Dark Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "applications": {
    "gecko": {
      "id": "darkmode-toggle-unique123@example.com"
    }
  }
}