Examine source code of Narrative Dark Mode

{
  "name": "Narrative Dark Mode",
  "version": "1.0",
  "description": "Dark Mode Extension for Narrative",
  "manifest_version": 2,
  "permissions": [
    "https://*/*",
    "activeTab",
    "tabs"
  ],
  "content_scripts": [
    {
      "matches": [
        "https://*.narrative.org/*"
      ],
      "css": [
        "dark_mode.css"
      ],
      "all_frames": true,
      "run_at": "document_start"
    }
  ],
  "web_accessible_resources": [
    "dark_mode.css"
  ]
}