You are given an array of `k` linked-lists `lists`, each linked-list is sorted in ascending order.
Merge all the linked-lists into one sorted linked-list and return it.
checklist Constraints
k == lists.length 0 <= k <= 10^4 0 <= lists[i].length <= 500 -10^4 <= lists[i][j] <= 10^4 lists[i] is sorted in ascending order. The sum of lists[i].length will not exceed 10^4.