Update README.md

Author: harmeetsingh11

Diff for: 2694-event-emitter/README.md

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-<h2><a href="https://leetcode.com/problems/event-emitter/">2694. Event Emitter</a></h2><h3>Medium</h3><hr><div><p>Design an <code>EventEmitter</code> class. This interface&nbsp;is similar (but with some differences) to the one found in Node.js or the Event Target interface of the DOM. The <code>EventEmitter</code> should allow for subscribing to events and emitting them.</p>
+<h2><a href="https://leetcode.com/problems/event-emitter/">2694. Event Emitter</a></h2><img src="https://img.shields.io/badge/Medium-FECC00" alt="Medium" /><hr><div><p>Design an <code>EventEmitter</code> class. This interface&nbsp;is similar (but with some differences) to the one found in Node.js or the Event Target interface of the DOM. The <code>EventEmitter</code> should allow for subscribing to events and emitting them.</p>
 
 <p>Your <code>EventEmitter</code> class should have the following two methods:</p>