buildTree = function(preorder, inorder) {
    const isBaseCase = !preorder.length || !inorder.length;
    if (isBaseCase) return null;

    return dfs(preorder, inorder);
}
https://leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/
Time O(N^2) | Space(H)
@param {number[]} preorder
@param {number[]} inorder
@return {TreeNode}