text: if (this.customElements) {
    try {
      customElements.define(
        "built-in",
        document.createElement("p").constructor,
        { extends: "p" }
      );
    } catch (_) {
      document.write(
        '<script src="//unpkg.com/@ungap/custom-elements-builtin"><\x2fscript>'
      );
    }
  } else {
    document.write(
      '<script src="//unpkg.com/document-register-element"><\x2fscript>'
    );
  }
  