docs(wordflip): instructions upgrade

subjects/wordflip/README.md

@@ -0,0 +1,47 @@
+## wordflip
+
+### Instructions
+
+Write a function `WordFlip()` that receives a `string` and returns it in reverse order.
+
+- Prints the Output followed by newline `\n`.
+- If the string is empty, return `Invalid Output`.
+- Ignore spaces if there are more than one space in between words and ignore all spaces at the edge of the `string`.
+
+### Expected function
+
+```go
+func WordFlip(str string) string {
+
+}
+```
+
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	fmt.Print(piscine.WordFlip("First second last"))
+	fmt.Print(piscine.WordFlip(""))
+	fmt.Print(piscine.WordFlip("     "))
+	fmt.Print(piscine.WordFlip(" hello  all  of  you! "))
+}
+```
+
+And its output:
+
+```console
+$ go run . | cat -e
+last second First$
+Invalid Output$
+$
+you! of all hello$
+```