add some leetcode questions

[Arisha2902]

@PRIYESHSINGH24, add a new solution to "LeetCode" problems.
Que no. 105. Construct Binary Tree from Preorder and Inorder Traversal( which is "medium" question
Que no. 897. Increasing Order Search Tree
Que no. Apply Transform Over Each Element in Array
Que no. 98. Validate Binary Search Tree