Add max function in 1004

Author: halfrost

website/content/ChapterFour/1000~1099/1004.Max-Consecutive-Ones-III.md

@@ -77,6 +77,13 @@ func longestOnes(A []int, K int) int {
 	return res
 }
 
+func max(a int, b int) int {
+	if a > b {
+		return a
+	}
+	return b
+}
+
 ```