subject(SumArray):add readme

subjects/arraysum/README.md

@@ -0,0 +1,41 @@
+## array-sum
+
+### Instructions
+
+Write a function that takes an array of numbers and returns the sum of all the numbers in the array.
+- If the array is empty, the function should return 0.
+
+### Expected function
+
+```go
+func ArraySum(numbers []int) int {
+    // your code here
+}
+```
+
+### Usage
+
+```go
+package main
+
+import (
+    "fmt"
+)
+
+func main(){
+    fmt.Println(ArraySum([]int{1,2,3,4,5}))
+    fmt.Println(ArraySum([]int{}))
+    fmt.Println(ArraySum([]int{-1,-2,-3,-4,-5}))
+    fmt.Println(ArraySum([]int{-1,2,3,4,-5}))
+}
+```
+
+and the output should be:
+
+```console
+$ go run . 
+15
+0
+-15
+3
+```