docs:(bezero): add missing space between line 5 and line 6

- upgrade instructions
- add missing import 'piscine'
- fix indentation

subjects/bezero/README.md

@@ -0,0 +1,42 @@
+## bezero
+
+### Instructions
+
+Write a function that takes a slice of integers as an argument and returns the same slice by initializing all the elements to 0.
+
+- If the slice is empty, return an empty slice.
+
+### Expected function
+
+```go
+func BeZero(slice []int) []int {
+
+}
+```
+
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	fmt.Println(piscine.BeZero([]int{1, 2, 3, 4, 5, 6}))
+	fmt.Println(piscine.BeZero([]int{}))
+}
+
+```
+
+And its output:
+
+```console
+$ go run .
+[0 0 0 0 0 0]
+[]
+```