Update exception handling in JavaScript roadmap (#1657)

content/roadmaps/106-javascript/content/107-javascript-control-flow/100-exception-handling/readme.md

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-# Exception handling
+# Exception Handling
+
+In JavaScript, all exceptions are simply objects. While the majority of exceptions are implementations of the global Error class, any old object can be thrown. With this in mind, there are two ways to throw an exception: directly via an Error object, and through a custom object. (excerpt from Rollbar)
+
+<BadgeLink colorScheme='yellow' badgeText='Read' href='https://rollbar.com/guides/javascript/how-to-throw-exceptions-in-javascript'>Throwing Exceptions in JavaScript</BadgeLink>