Examine source code of Instabar

{
  "description": "Show scrollbar on Instagram",
  "manifest_version": 2,
  "name": "Instabar",
  "version": "1.1",
  "content_scripts": [
    {
      "matches": [
        "https://www.instagram.com/*"
      ],
      "css": [
        "content-script.css"
      ],
      "run_at": "document_start"
    }
  ],
  "applications": {
    "gecko": {
      "strict_min_version": "57.0a1"
    }
  }
}