1: Add Rust track exercise "Hello World".

Created by  Aaw9nJhsNmfzFih9mKyNw9mV8CgERXJkRa1kK1Kx3LQH  on August 15, 2021
FS63YMFJXLOXEDFKD5IETLB4XI6EUZOTRVHXPZVEZBPSFAQRZWNAC
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