Examine source code of Dexter dark mode

{
  "manifest_version": 2,
  "name": "Dexter dark mode",
  "version": "0.1",
  "description": "Just a small project/theme for my schools website :)",
  "content_scripts": [
    {
      "matches": [
        "*://dexter.live/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "content.css"
      ]
    }
  ]
}