docs(printandmiss): fix instructions

- add missing title header '#'
- add missing import 'piscine
- format indentation

subjects/printandmiss/README.md

@@ -0,0 +1,49 @@
+## printandmiss
+
+### Instructions
+
+Write a function called `PrintAndMiss()` that takes a `string` and an `int` as an argument. The function should move through the `string` in sets determined by the `int`, printing the first set, omitting the second, printing the third, and so on, in a 'print' and 'miss' fashion until the end of the `string` is reached. Return a `string` containing the printed characters.
+
+- If the `string` is empty or the `int` is negative return `Invalid Output` followed by newline `\n`.
+- If the `int` is `0` return the `string` followed by a newline `\n`.
+
+### Expected function
+
+```go
+func PrintAndMiss(arg string, num int) string {
+
+}
+```
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	fmt.Print(piscine.PrintAndMiss("123456789", 3))
+	fmt.Print(piscine.PrintAndMiss("abcdefghijklmnopqrstuvwyz", 3))
+	fmt.Print(piscine.PrintAndMiss("", 3))
+	fmt.Print(piscine.PrintAndMiss("hello you all ! ", 0))
+	fmt.Print(piscine.PrintAndMiss("what is your name?", 0))
+	fmt.Print(piscine.PrintAndMiss("go Exercise Print and Miss", -5))
+}
+```
+
+And its output:
+
+```console
+$ go run . | cat -e
+123789$
+abcghimnostuz$
+Invalid Output$
+hello you all ! $
+what is your name?$
+Invalid Output$
+```