Add ES6 syntax to Challenge' solution (#36367)

* ES6 syntax

Added ES6 syntax to challenge' solution.

* Add ES6 solution to challenge

An optional way to solve the challenge using ES6 arrow functions

guide/english/certifications/javascript-algorithms-and-data-structures/object-oriented-programming/use-an-iife-to-create-a-module/index.md

@@ -45,3 +45,21 @@ let funModule = (function() {
 })();
 
 ```
+
+### Solution 2
+
+If using ES6, the same can be rewritten as:
+
+```javascript
+let funModule = ( () => {
+  return {
+    isCuteMixin: (obj) => {
+      obj.isCute = () => { true; };
+    },
+    singMixin: (obj) => {
+      obj.sing = () => { console.log("Singing to an awesome tune"); }
+    }
+
+  }
+})();
+```

guide/english/certifications/javascript-algorithms-and-data-structures/object-oriented-programming/use-closure-to-protect-properties-within-an-object-from-being-modified-externally/index.md

@@ -21,3 +21,14 @@ function Bird() {
 }
 
 ```
+
+### Solution 2
+
+In ES6 syntax we can make the function a bit less verbose:
+
+```
+function Bird() {
+  let weight = 15;
+  this.getWeight = () => weight;  
+}
+```