Max Area of Island

You are given an `m x n` binary matrix `grid`. An island is a group of `1`'s (representing land) connected **4-directionally** (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water. The **area** of an island is the number of cells with a value `1` in the island. Return _the maximum **area** of an island in _`grid`. If there is no island, return `0`.   **Example 1:** **Input:** grid = [[0,0,1,0,0,0,0,1,0,0,0,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,1,1,0,1,0,0,0,0,0,0,0,0],[0,1,0,0,1,1,0,0,1,0,1,0,0],[0,1,0,0,1,1,0,0,1,1,1,0,0],[0,0,0,0,0,0,0,0,0,0,1,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,0,0,0,0,0,0,1,1,0,0,0,0]] **Output:** 6 **Explanation:** The answer is not 11, because the island must be connected 4-directionally. ``` **Example 2:** **Input:** grid = [[0,0,0,0,0,0,0,0]] **Output:** 0 ```   **Constraints:** - `m == grid.length` - `n == grid[i].length` - `1 <= m, n <= 50` - `grid[i][j]` is either `0` or `1`.