Examine source code of Site CSS

{
  "manifest_version": 3,
  "name": "__MSG_extension_name__",
  "description": "__MSG_extension_description__",
  "version": "1.1",
  "default_locale": "en",
  "permissions": [
    "scripting",
    "storage"
  ],
  "host_permissions": [
    "<all_urls>"
  ],
  "background": {
    "service_worker": "bg.js",
    "scripts": [
      "bg.js"
    ]
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{33d4cb96-5745-40eb-8b85-89158df1d372}",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  },
  "options_ui": {
    "page": "options.html",
    "open_in_tab": true
  },
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "all_frames": true,
      "run_at": "document_start",
      "js": [
        "onload.js"
      ]
    }
  ],
  "icons": {
    "16": "assets/icon16.png",
    "24": "assets/icon24.png",
    "32": "assets/icon32.png",
    "48": "assets/icon48.png",
    "128": "assets/icon128.png"
  },
  "action": {}
}