raw string literals

If a string needs to include lots of escape sequences, raw string literals can be used.

This:

const std::string help =
    "\n  Usage: wc [OPTIONS]\n\n"
    "  Options:\n"
    "    -h,--help                   Print this help message and exit\n";

can also be written as:

const std::string help = R"(
  Usage: wc [OPTIONS]

  Options:
    -h,--help                   Print this help message and exit
  )";

More on:
https://docs.microsoft.com/en-us/cpp/cpp/string-and-character-literals-cpp?view=msvc-170#raw-string-literals-c11