feat(piscine-go): add README.md for new go exercise rockandroll

subjects/rockandroll/README.md

@@ -0,0 +1,45 @@
+## rockandroll
+
+### Instructions
+
+Write a function called `RockAndRoll` that takes an integer and returns a string.
+
+- If the number is divisible by 2, print `rock` followed by a newline `\n`.
+- If the number is divisible by 3, print `roll` followed by a newline `\n`.
+- If the number is divisible by 2 and 3, print `rock and roll` followed by a newline `\n`.
+
+### Expected function
+
+```go
+func RockAndRoll(n int) string {
+
+}
+```
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+	"fmt"
+	"strconv"
+)
+
+func main() {
+	fmt.Println(RockAndRoll(4))
+	fmt.Println(RockAndRoll(9))
+	fmt.Println(RockAndRoll(6))
+}
+```
+And its output:
+
+```go
+rock$
+$
+roll$
+$
+rock and roll$
+$
+```