Add event loop content (#1784)

* Update 100-event-loop.md

* Update content/roadmaps/107-nodejs/content/104-nodejs-async-programming/100-event-loop.md

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

content/roadmaps/107-nodejs/content/104-nodejs-async-programming/100-event-loop.md

@@ -1 +1,11 @@
-# Event loop
+# Event Loop
+
+The Event Loop is one of the most critical aspects of 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.
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+
+<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>
+<BadgeLink badgeText='Course' colorScheme='green' href='https://www.coursera.org/lecture/secure-full-stack-mean-developer/the-node-js-event-loop-j5fbT'>The Node.js Event Loop</BadgeLink>
+<BadgeLink badgeText='Watch' href='https://www.youtube.com/watch?v=6YgsqXlUoTM'>The Complete Node js: The Node js Event Loop</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://nodejs.dev/en/learn/the-nodejs-event-loop/'>The NodeJS Event loop</BadgeLink>