docs(sortBydir): Adding the subject of exercice sortBydir for js piscine

subjects/sortBydir/README.md

@@ -0,0 +1,40 @@
+## sortBydir
+
+### Instructions
+
+Create a function that order an array of numbers,it should receive a dir parameter which has with two possible values 'asc' or 'desc', and return a new array ordered ascendingly or descendingly respectively. 
+
+If no dir parameter is set it should assume 'asc' by default. 
+
+If the dir parameter has an invalid value, return false.
+
+If the values of the array is not an integer, return false.
+
+
+### Expected Function
+
+```js
+function sortReloaded(arrayIntg,dir)
+
+```
+
+### Usage
+
+Here is a program to test your function.
+
+```js
+const inputArray = [4, 2, 8, 1, 5];
+const ascendingResult = orderArray(inputArray);
+const descendingResult = orderArray(inputArray, 'desc');
+console.log(ascendingResult);
+console.log(descendingResult);
+```
+
+And its output
+
+```console
+$ node index.js
+[1, 2, 4, 5, 8]
+[8, 5, 4, 2, 1]
+$
+```