Fix : "error: incomplete type ‘std::numeric_limits<unsigned char>’ "

[grybouilli]

Fix description

Add header to fix "error: incomplete type ‘std::numeric_limits’ used in nested name specifier"

Reproduce bug

To reproduce, use the code from README.md :

#include <qrcode/qrcode.h>
#include <iostream>

int main()
{
    using namespace qrcode;
    using namespace std::literals;
    
    auto symbol = qr::make_symbol("Hello World!"sv, qr::error_correction::level_L).value();

    auto count = 0;
    for (auto i : views::horizontal(symbol))
    {
        std::cout << (i ? '#' : ' ');
        ++count;
        if (count % width(symbol) == 0)
            std::cout << '\n';
    }
}

Compile with (assuming code in file test.cpp in repo folder):

g++ test.cpp -std=c++20 -I./include

with g++ 13.3.0 gives:

include/qrcode/code/byte_view.h: In function ‘constexpr auto qrcode::code::detail::bits_per_byte()’:
include/qrcode/code/byte_view.h:39:51: error: incomplete type ‘std::numeric_limits<unsigned char>’ used in nested name specifier
   39 |         return std::numeric_limits<std::uint8_t>::digits;
      | 

[ixik-melissa]

Thank you very much for pointing that out.
Fixed in PR #13.