38: Add solution for Rust track exercise "Reverse String".

Created by  Aaw9nJhsNmfzFih9mKyNw9mV8CgERXJkRa1kK1Kx3LQH  on October 9, 2021
FOFFISFHQTXCKPT2XBYQ5HJJOP47UKCNYTKLTJ2FWXXJGURXVQFAC
In channels
main
Change contents