docs: Add readme for ascii subject

subjects/ascii/README.md

@@ -0,0 +1,38 @@
+## ascii
+
+### Instructions
+
+Write a function that receives a string and returns a slice with the ASCII values of its characters.
+
+### Expected function
+
+```go
+func Ascii(str string) []byte {
+
+}
+```
+
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+    "piscine"
+    "fmt"
+)
+
+func main() {
+    l := piscine.Ascii("Hello")
+    fmt.Println(l)
+}
+```
+
+And its output:
+
+```console
+$ go run .
+[104 101 108 108 111]
+```