Toeplitz Matrix

Given an m x n matrix, return true if the matrix is Toeplitz. Otherwise, return false.

A matrix is Toeplitz if every diagonal from top-left to bottom-right has the same element. In other words, for every cell matrix[i][j] (where i > 0 and j > 0), it must equal matrix[i-1][j-1].

You need to implement a function that checks this property efficiently.