Rayon find_map_any() demonstration program

This small program shows how effective and simple Rust's Rayon crate find_map_any() can be used to utilize all CPU cores.

P.S.: The factorize_iterative() function of mine was an experiment to try out find_map_any() with something not immediately trivial, but is of course not meant for production use. Better and faster algorithms exist, also in crates.io.