Examine source code of Dark Duolingo

{
  "name": "Dark Duolingo",
  "short_name": "Dark Duo",
  "description": "Darken Duolingo's UI to play without burning your retinas!  This extension affects Duolingo's style only, not its functionality.",
  "author": "Cory der Große",
  "homepage_url": "https://corydergrosse.github.io",
  "version": "1.15",
  "manifest_version": 2,
  "icons": {
    "16": "icons/icon_16.png",
    "48": "icons/icon_48.png",
    "96": "icons/icon_96.png",
    "128": "icons/icon_128.png"
  },
  "content_scripts": [
    {
      "matches": [
        "*://*.duolingo.com/*"
      ],
      "css": [
        "darkDuolingo.css"
      ]
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{febf0f21-dedf-41f9-95da-8c91fca61228}"
    }
  }
}