array_append(a1, @rest a2, ...)
Return a new array with all the elements of the arrays a2, ... appended to the array a1.
array_append(#[1, 2, 3], #[4, 5, 6], #[100])
// #[1, 2, 3, 4, 5, 6, 100]
array_append(#[1, 2, 3])
// #[1, 2, 3]