removeNthFromEnd = function(head, n) {
    const sentinel = new ListNode();

    sentinel.next = head;

    const fast = moveFast(sentinel, n);   /* Time O(N) */
    const slow = moveSlow(sentinel, fast);/* Time O(N) */

    slow.next = slow.next.next || null;

    return sentinel.next;
}
https://leetcode.com/problems/remove-nth-node-from-end-of-list/
Time O(N) | Space O(N)
@param {ListNode} head
@param {number} n
@return {ListNode}