1: Add Rust track exercise "Hello World".

Created by  Aaw9nJhsNmfzFih9mKyNw9mV8CgERXJkRa1kK1Kx3LQH  on October 10, 2021
OSLWPPDFD3CGOHCXJLCIU7NLOGSMCMUFD5EREMR4EWPP3JMWN7EAC
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