docs(digitlen): fix subject

- fix file name
 - format exercise title
 - upgrade instructions
 - add missing import piscine
 - fix white-sapces and indentation

subjects/digitlen/README.md

@@ -0,0 +1,46 @@
+## digitlen
+
+### Instructions
+
+Write a function `DigitLen()` that takes two integers as arguments and returns the number of digits in the first `int` by the base of the second `int`.
+
+- The second `int` must be between ***2*** and ***36***. If not, the function returns `-1`.
+- If the first `int` is negative, reverse the sign and count the digits.
+
+### Expected function
+
+```go
+func DigitLen(n, base int) int {
+
+}
+```
+
+### Usage
+
+Here is a possible program to test your function:
+
+```go
+package main
+
+import (
+	"fmt"
+	"piscine"
+)
+
+func main() {
+	fmt.Println(piscine.DigitLen(100, 10))
+	fmt.Println(piscine.DigitLen(100, 2))
+	fmt.Println(piscine.DigitLen(-100, 16))
+	fmt.Println(piscine.DigitLen(100, -1))
+}
+```
+
+And its output:
+
+```console
+$ go run . | cat -e
+3
+7
+2
+-1
+```

subjects/digitlen/READMED.md

@@ -1,44 +0,0 @@
-## digit-len
-
-### Instructions 
-
-Write a function that takes two integers and returns the number of digits in the first integer by the base of the second integer.
-- The second integer must be between 2 and 36. if not, the function returns `-1`.
-- If the first integer is negative , reverse the sign and count the digits.
-
-
-### Expected function
-
-```go
-func DigitLen(n, base int) int {
-
-}
-```
-
-### Usage
-
-Here is a possible program to test your function :
-
-```go
-package main
-
-import "fmt"
-
-func main(){
-    fmt.Println(DigitLen(100, 10))
-    fmt.Println(DigitLen(100, 2))
-    fmt.Println(DigitLen(-100, 16))
-    fmt.Println(DigitLen(100, -1))
-
-}
-```
-
-And its output :
-
-```console
-$ go run . | cat -e
-3
-7
-2
--1
-```