message: in debug log messages, escape the quotation mark for better readability.
diff: @@ -39,6 +39,8 @@ inline std::string escape(char32_t ch)
  return "\\r";
  case '\n':
  return "\\n";
  + case '"':
  + return "\\\"";
  default:
  if (ch <= 0xFF && std::isprint(ch))
  return fmt::format("{}", static_cast<char>(ch));
  