Examine source code of Focus Flow: Thumbnail Mask

{
  "manifest_version" : 3 ,
  "name" : "Focus Flow: Thumbnail Mask",
  "version" : "1.0.0",
  "description" : "Hide and customize YouTube thumbnails to reduce visual clutter and browse with intention.",
  "browser_specific_settings": {
    "gecko": {
      "id": "focusflow@yourdomain.com",
      "strict_min_version": "109.0",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "permissions" : [
    "storage" 
  ],
  "host_permissions" : [
    "https://www.youtube.com/*" 
  ],
  "content_security_policy" : {
    "extension_pages": "script-src 'self'; object-src 'self';"
  },
  "action" : {
    "default_popup" : "popup.html",
    "default_icon" : {
      "16" : "icons/icon16.png",
      "48" : "icons/icon48.png",
      "128" : "icons/icon128.png"
    }
  },
  "content_scripts" : [
    {
      "matches" : [
        "https://www.youtube.com/*" 
      ],
      "css" : [
        "content.css" 
      ],
      "js" : [
        "content.js" 
      ],
      "run_at" : "document_start" 
    }
  ],
  "icons" : {
    "16" : "icons/icon16.png",
    "48" : "icons/icon48.png",
    "128" : "icons/icon128.png"
  }
}