`cpp_str()` impossible to be used with `u8string`

[patrolez]

Hello,
while using object with tiny_utf8::u8string type there is a problem with compilation while cpp_str() and/or cpp_str_bom() is being in use by a code.

Compiler: g++-10, 10.3.0-1ubuntu1~20.04
With -std=c++2a flag.

../../libs/tiny-utf8/include/tinyutf8/tinyutf8.h:3404:46: error: conversion from ‘basic_string<char>’ to non-scalar type ‘basic_string<char8_t>’ requested
 3404 |   std::basic_string<data_type> result = std::string( size() + 3 , ' ' );
      |                                              ^~~~~~~~~~~~~~~~~~~~~~~~~~

tiny-utf8/include/tinyutf8/tinyutf8.h

Line 3404 in cab426c

std::basic_string<data_type> result = std::string( size() + 3 , ' ' );

[DuffsDevice]

Hi Patryk,

Thanks for submitting a bug report, I'll fix it right away!

[DuffsDevice]

Let me know, if everything works for you now. If not, please feel free to re-open the ticket :)