Examine source code of Night Mode Toggle

{
  "manifest_version": 2,
  "name": "Night Mode Toggle",
  "version": "1.0",
  "description": "Toggle a dark reading mode for any website.",
  "icons": {
    "48": "icon.png"
  },
  "permissions": [
    "activeTab",
    "tabs"
  ],
  "browser_action": {
    "default_icon": "icon.png",
    "default_title": "Toggle Night Mode"
  },
  "background": {
    "scripts": [
      "background.js"
    ]
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "content-script.js"
      ],
      "run_at": "document_idle"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{f4419794-714e-4655-b625-f98765a8b3ff}"
    }
  }
}