Removes first value.
Alternatives: shift, shift$.
Similar: push, pop, shift, unshift.
This is part of package extra-array.
array.shift$(x);
// x: an array (updated)
// → x
const array = require("extra-array");
var x = [1, 2, 3];
array.shift$(x);
// [2, 3]
x;
// [2, 3]
var x = [1, 2, 3, 4];
array.shift$(x);
// [2, 3, 4]