Join vector of integers

---

examples/vectors/join-integers/src/main.rs

fn main() {
    let integers = vec![1, 2, 3];
    println!("{:?}", integers);

    let joined = integers
        .iter()
        .map(|num| num.to_string())
        .collect::<Vec<_>>()
        .join(",");
    println!("{}", joined);
    assert_eq!(joined, "1,2,3");
}

[1, 2, 3]
1,2,3