Examine source code of YouTube Grid Customizer

{
  "manifest_version": 3,
  "name": "YouTube Grid Customizer",
  "version": "2.0",
  "description": "Pick or auto‑fit how many videos appear per row on YouTube",
  "action": {
    "default_popup": "popup.html"
  },
  "permissions": [
    "storage"
  ],
  "host_permissions": [
    "*://www.youtube.com/*"
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "{d4cbb48e-8e10-443d-b9a6-e4cefce04476}"
    }
  },
  "content_scripts": [
    {
      "matches": [
        "*://www.youtube.com/*"
      ],
      "js": [
        "content.js"
      ],
      "css": [
        "styles.css"
      ],
      "run_at": "document_idle"
    }
  ]
}