Examine source code of Nifty Css Override

{
  "manifest_version": 3,
  "name": "CSS Override",
  "version": "1.0",
  "description": "CSS Override: Inject custom CSS.",
  "action": {
    "default_popup": "popup.html",
    "default_icon": "css_override.png"
  },
  "icons": {
    "128": "css_override.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "crystalduncan6741@outlook.com",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}