Add Dep: Use FMT library for formatting

[WSLUser]

https://github.com/fmtlib/fmt :
{fmt} is an open-source formatting library for C++. It can be used as a safe and fast alternative to (s)printf and iostreams. This project makes considerable use of iostreams, therefore it's highly likely to hugely benefit from the addition of this library. To see example usage, take a look at the Windows Terminal repo.