Feat: Add solution of contains-duplicate

Author: easyone

contains-duplicate/easyone-jwlee.go

@@ -0,0 +1,10 @@
+func containsDuplicate(nums []int) bool {
+	m := make(map[int]int)
+	for _, num := range nums {
+		if _, ok := m[num]; ok {
+			return true
+		}
+		m[num] = num
+	}
+	return false
+}