Add JS/TS warnings to concurrent clients stage

Author: rohitpaulk

course-definition.yml

@@ -488,6 +488,22 @@ stages:
     description_md: |-
       In this stage, you'll add support for concurrent connections.
 
+      {{#lang_is_javascript}}
+      In most languages, you'd need to either use threads or implement an
+      [Event Loop](https://en.wikipedia.org/wiki/Event_loop) to do this. In JavaScript however, since [the concurrency
+      model itself is based on an event loop](https://developer.mozilla.org/en-US/docs/Web/JavaScript/EventLoop), most
+      standard library functions are designed to support this kind of concurrent behaviour out of the box. **It is very
+      likely that the code you had for the previous stage will pass this stage without any changes!**
+      {{/lang_is_javascript}}
+
+      {{#lang_is_typescript}}
+      In most languages, you'd need to either use threads or implement an
+      [Event Loop](https://en.wikipedia.org/wiki/Event_loop) to do this. In TypeScript however, since [the concurrency
+      model itself is based on an event loop](https://developer.mozilla.org/en-US/docs/Web/JavaScript/EventLoop), most
+      standard library functions are designed to support this kind of concurrent behaviour out of the box. **It is very
+      likely that the code you had for the previous stage will pass this stage without any changes!**
+      {{/lang_is_typescript}}
+
       ### Tests
 
       The tester will execute your program like this: