Add fast_io (faster input/output library) (fffaraz#1521)

Author: toge

README.md

@@ -1151,6 +1151,7 @@ A curated list of awesome C++ (or C) frameworks, libraries, resources, and shiny
 * [emio](https://github.com/Viatorus/emio) - A safe and fast high-level and low-level character input/output library. [MIT]
 * [faker-cxx](https://github.com/cieslarmichal/faker-cxx) - C++20 Faker library for generating fake (but realistic) data for testing and development. [MIT]
 * [FastFormat](http://www.fastformat.org) - Fast, Safe C++ Formatting inspired by log4j and Pantheios. [Simplified BSD]
+* [fast_io](https://github.com/cppfastio/fast_io) - Significantly faster input/output for C++20. [MIT]
 * [fccf](https://github.com/p-ranav/fccf) - A command-line tool that recursively searches a directory to find C/C++ source code matching a search string. [MIT]
 * [{fmt}](https://github.com/fmtlib/fmt) :zap: - Small, safe and fast formatting library for C++. [Simplified BSD] [website](https://fmt.dev)
 * [gcc-poison](https://github.com/leafsr/gcc-poison) - A simple header file for developers to ban unsafe C/C++ functions from applications.