Add greedy decoding to example 'simple'

[joneavila]

Run the example following the README: cargo run --release --bin simple -- --prompt "The way to kill a linux process is" hf-model TheBloke/Llama-2-7B-GGUF llama-2-7b.Q4_K_M.gguf

Before modification:

 The way to kill a linux process is给给给给给给给给给给给给给给给给给给给给给给给给

After modification:

 The way to kill a linux process is to send it a SIGKILL signal.
The way to kill a windows process is to send it a S