Given an array of integers `heights` representing the histogram's bar heights where the width of each bar is `1`, return the area of the largest rectangle in the histogram.
Example 1
Input:heights = [2,1,5,6,2,3]
Output:10
Explanation:The largest rectangle is the bars at indices 2 and 3 (heights 5 and 6), giving area 2 × 5 = 10.