feat:Add IsNegative subject

subjects/is-negative/README.md

@@ -0,0 +1,58 @@
+##  is-negative
+
+### Instructions
+
+# IS-Negative
+
+### Instruction 
+
+Write a function named `IsNegative()` that defines if a number (You should check if it's a number) is negative or positive.
+
+     Your function print P if the number is positive
+     Your function print F if the number is negative
+     For the number is zero print 0.
+     Any input other than number should print !
+     Your program should always print ('\n')at the end of the output.
+
+### Expected function
+
+```go
+func IsNegative(str string){
+    //code
+}
+```
+
+### Usage
+
+```go
+package main
+
+import (
+	"os"
+    "piscine"
+	"fmt"
+)
+
+func main() {
+	argument := os.Args[1:]
+	IsNegative(argument[0])
+}
+```
+And its output:
+
+```console
+$ go run . | cat -e
+!$
+$ go run . "7" | cat -e
+P$
+$ go run . "-9" | cat -e
+N$
+$ go run . a | cat -e
+!$
+$ go run . "-552" | cat -e
+N$
+$ go run . "58" | cat -e
+P$
+$ go run . "Hello World" | cat -e
+!$
+```