You are given an `m x n` binary matrix `grid`. An **island** is a group of `1`s (land) connected 4-directionally (horizontal or vertical).
Return the **area** of the largest island. If there is no island, return `0`.
Example 1
Input:grid = [[0,0,1,0],[0,1,1,0],[0,0,0,0]]
Output:3
Explanation:The single island has 3 connected cells.
Example 2
Input:grid = [[0,0],[0,0]]
Output:0
Explanation:No land cells.
Constraints
- m == grid.length
- n == grid[i].length
- 1 <= m, n <= 50
- grid[i][j] is 0 or 1