Examine source code of Dark Mode Toggle

{
  "manifest_version": 2,
  "name": "Dark Mode Toggle",
  "version": "1.0",
  "description": "Toolbar button to toggle dark mode",
  "icons": {
    "48": "icons/toggle.svg",
    "96": "icons/toggle.svg"
  },
  "browser_action": {
    "default_icon": "icons/toggle.svg",
    "default_title": "Toggle dark mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "permissions": [
    "browserSettings"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f5946e47-e4f1-46b8-aee6-7b4f14df3f7f}"
    }
  }
}