Add setInterval content (#1861)

* Update 106-set-interval.md

* Update content/roadmaps/107-nodejs/content/104-nodejs-async-programming/106-set-interval.md

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

content/roadmaps/107-nodejs/content/104-nodejs-async-programming/106-set-interval.md

@@ -1 +1,9 @@
-# Set interval
+# setInterval
+
+The `setInterval()` method helps us to repeatedly execute a function after a fixed delay. It returns a unique interval ID which can later be used by the `clearInterval()` method, which stops further repeated execution of the function. 
+
+`setInterval()` is similar to setTimeout, with a difference. Instead of running the callback function once, it will run it forever, at the specific time interval you specify (in milliseconds):
+
+<ResourceGroupTitle>Free Content</ResourceGroupTitle>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://javascript.info/settimeout-setinterval'>Scheduling: setTimeout and setInterval</BadgeLink>
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://www.geeksforgeeks.org/what-is-setinterval-in-javascript/'>What is the use of setInterval() method in Node.js?</BadgeLink>