Examine source code of 444.hu addon

{
  "manifest_version": 2,
  "name": "444.hu Addon",
  "version": "0.1.0",
  "description": "Eltavolitja a kunyeralasdobozt",
  "content_scripts": [
    {
      "css": [
        "styles.css"
      ],
      "matches": [
        "https://444.hu/*"
      ]
    }
  ]
}