Function utf8to32

third-party/utf8cpp/source/utf8/cpp17.h:63–68

    }

    inline std::u32string utf8to32(std::string_view s)
    {
        std::u32string result;
        utf8to32(s.begin(), s.end(), std::back_inserter(result));
        return result;
    }

    inline std::size_t find_invalid(std::string_view s)
    {