Add solution #2621

Author: JoshCrozier

Diff for: README.md

@@ -364,6 +364,7 @@
 2618|[Check if Object Instance of Class](./2618-check-if-object-instance-of-class.js)|Medium|
 2619|[Array Prototype Last](./2619-array-prototype-last.js)|Easy|
 2620|[Counter](./2620-counter.js)|Easy|
+2621|[Sleep](./2621-sleep.js)|Easy|
 2629|[Function Composition](./2629-function-composition.js)|Easy|
 3392|[Count Subarrays of Length Three With a Condition](./3392-count-subarrays-of-length-three-with-a-condition.js)|Easy|
 3396|[Minimum Number of Operations to Make Elements in Array Distinct](./3396-minimum-number-of-operations-to-make-elements-in-array-distinct.js)|Easy|

Diff for: solutions/2621-sleep.js

@@ -0,0 +1,16 @@
+/**
+ * 2621. Sleep
+ * https://leetcode.com/problems/sleep/
+ * Difficulty: Easy
+ *
+ * Given a positive integer `ms`, write an asynchronous function that
+ * sleeps for `ms` milliseconds. It can resolve any value.
+ */
+
+/**
+ * @param {number} ms
+ * @return {Promise}
+ */
+async function sleep(ms) {
+  return new Promise((resolve) => setTimeout(resolve, ms));
+}