Rotting Oranges

You are given an `m x n` `grid` where each cell can have one of three values: - `0` representing an empty cell, - `1` representing a fresh orange, or - `2` representing a rotten orange. Every minute, any fresh orange that is **4-directionally adjacent** to a rotten orange becomes rotten. Return _the minimum number of minutes that must elapse until no cell has a fresh orange_. If _this is impossible, return_ `-1`.   **Example 1:** **Input:** grid = [[2,1,1],[1,1,0],[0,1,1]] **Output:** 4 ``` **Example 2:** **Input:** grid = [[2,1,1],[0,1,1],[1,0,1]] **Output:** -1 **Explanation:** The orange in the bottom left corner (row 2, column 0) is never rotten, because rotting only happens 4-directionally. ``` **Example 3:** **Input:** grid = [[0,2]] **Output:** 0 **Explanation:** Since there are already no fresh oranges at minute 0, the answer is just 0. ```   **Constraints:** - `m == grid.length` - `n == grid[i].length` - `1 <= m, n <= 10` - `grid[i][j]` is `0`, `1`, or `2`.