Mutable vector of numbers, append (push) values

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• We can make a vector mutable by using the mut keyword.
• We can append an element to the end of the vector using the push method.

examples/vectors/mutable-numbers-vector/src/main.rs

fn main() {
    let mut numbers = vec![10, 11, 12];
    println!("{}", numbers.len());
    println!("{:?}", numbers);

    numbers.push(23);

    println!("{}", numbers.len());
    println!("{:?}", numbers);
}