Function is_structured

src/json.hpp:20614–20617

@brief return whether type is structured @sa https://json.nlohmann.me/api/basic_json/is_structured/

    /// @brief return whether type is structured
    /// @sa https://json.nlohmann.me/api/basic_json/is_structured/
    constexpr bool is_structured() const noexcept
    {
        return is_array() || is_object();
    }

    /// @brief return whether value is null
    /// @sa https://json.nlohmann.me/api/basic_json/is_null/