feat: solution for exercise 13_variadic (#117)

Author: thearpankumar

internal/exercises/solutions/13_variadic/variadic.go

@@ -0,0 +1,10 @@
+package variadic
+
+// Sum returns the sum of any number of integers
+func Sum(nums ...int) int {
+	total := 0
+	for _, num := range nums {
+		total += num
+	}
+	return total
+}