Function add

src/ArduinoJson/Variant/VariantRefBase.hpp:109–111

  // https://arduinojson.org/v7/api/jsonvariant/add/
  template <typename T, enable_if_t<!is_same<T, JsonVariant>::value, int> = 0>
  T add() const {
    return add<JsonVariant>().template to<T>();
  }

  // Appends a new (null) element to the array.
  // Returns a reference to the new element.