Add largestOverlap function for image comparison

Implement function to calculate largest overlap between two images.

Author: jyoung2419

leetcode3/정진영/835. Image Overlap

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+/**
+ * @param {number[][]} img1
+ * @param {number[][]} img2
+ * @return {number}
+ */
+var largestOverlap = function(img1, img2) {
+    let count = 0;
+    let max = 0;
+    
+    for (let i = 0; i<img1.length; i++){
+        for (let j = 0; j<img1.length; j++){
+            if (img1[i][j] == 1) {
+
+            }
+        }
+    }
+
+    max = Math.max(max, count);
+};