Examine source code of Labels!

{
  "name": "Labels",
  "description": "A Label Extension. Play with it!",
  "version": "1.0",
  "manifest_version": 3,
  "icons": {
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  },
  "action": {
    "default_popup": "index.html",
    "default_icon": {
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "extensionsyo@addons.mozilla.org",
      "data_collection_permissions": {
        "required": [
          "none"
        ]
      }
    }
  }
}