Examine source code of Change Backgroundolor

{
  "manifest_version": 3,
  "name": "Change Background Color",
  "version": "1.0",
  "description": "Sets a dark background and light text on every page.",
  "permissions": [],
  "host_permissions": [
    "<all_urls>"
  ],
  "content_scripts": [
    {
      "matches": [
        "<all_urls>"
      ],
      "js": [
        "change-bg.js"
      ],
      "run_at": "document_end"
    }
  ],
  "browser_specific_settings": {
    "gecko": {
      "id": "change-background@example.com"
    }
  }
}