learn: add Asynchronous JS link (#7509)

* About Asynchronous JS

Signed-off-by: Shivsingh15 <[email protected]>

* remove extra space and back Slash from the Async Link

Signed-off-by: Shivsingh15 <[email protected]>

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Signed-off-by: Shivsingh15 <[email protected]>

Author: Shivsingh15

apps/site/pages/en/learn/getting-started/how-much-javascript-do-you-need-to-know-to-use-nodejs.md

@@ -24,6 +24,7 @@ As a beginner, it's hard to get to a point where you are confident enough in you
 - [Template Literals](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Template_literals)
 - [Strict Mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode)
 - [ECMAScript 2015 (ES6) and beyond](/learn/getting-started/ecmascript-2015-es6-and-beyond)
+- [Asynchronous JavaScript](https://developer.mozilla.org/en-US/docs/Learn_web_development/Extensions/Async_JS)
 
 With those concepts in mind, you are well on your road to become a proficient JavaScript developer, in both the browser and in Node.js.