Substring Anagrams

Given two strings, s and t , both consisting of lowercase English letters, return the number of substrings in s that are anagrams of t.

An anagram is a word or phrase formed by rearranging the letters of another word or phrase, using all the original letters exactly once.

Example:

Input: s = 'caabab', t = 'aba'
Output: 2

Explanation: There is an anagram of t starting at index 1 ("caabab") and another starting at index 2 ("caabab")