Add event loop content (#1679)

* Update 100-event-loop.md

* Update content/roadmaps/106-javascript/content/112-javascript-asynchronous-javascript/100-event-loop.md

Co-authored-by: Kamran Ahmed <kamranahmed.se@gmail.com>

content/roadmaps/106-javascript/content/112-javascript-asynchronous-javascript/100-event-loop.md

@@ -1 +1,6 @@
-# Event loop
+# Event Loop
+
+The Event Loop is one of the most important aspects to understand about Node.js. Why is this so important? Because it explains how Node.js can be asynchronous and have non-blocking I/O, it explains the "killer feature" of Node.js, which made it this successful.
+
+<BadgeLink colorScheme="yellow" badgeText="Read" href="https://nodejs.dev/en/learn/the-nodejs-event-loop/">The Node.Js Event Loop</BadgeLink>
+<BadgeLink colorScheme="yellow" badgeText="Read" href="https://dev.to/lydiahallie/javascript-visualized-event-loop-3dif">JavaScript Visualized: Event Loop</BadgeLink>