Examine source code of githeader-contain

{
  "manifest_version": 2,
  "name": "githeader-contain",
  "version": "0.0.12",
  "description": "Almost useless extension that forces the new Github header to stay in the center of the screen like the rest of the site",
  "content_scripts": [
    {
      "matches": [
        "*://github.com/*"
      ],
      "css": [
        "css/content-script.css"
      ],
      "run_at": "document_start"
    }
  ],
  "icons": {},
  "permissions": []
}