feat: add js solution to lc problem: No.2621 (#3341)

Author: AE-Hertz

solution/2600-2699/2621.Sleep/README.md

@@ -70,6 +70,23 @@ async function sleep(millis: number): Promise<void> {
  */
 ```
 
+#### JavaScript
+
+```js
+/**
+ * @param {number} millis
+ * @return {Promise}
+ */
+async function sleep(millis) {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/2600-2699/2621.Sleep/README_EN.md

@@ -67,6 +67,23 @@ async function sleep(millis: number): Promise<void> {
  */
 ```
 
+#### JavaScript
+
+```js
+/**
+ * @param {number} millis
+ * @return {Promise}
+ */
+async function sleep(millis) {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

solution/2600-2699/2621.Sleep/Solution.js

@@ -0,0 +1,12 @@
+/**
+ * @param {number} millis
+ * @return {Promise}
+ */
+async function sleep(millis) {
+    return new Promise(r => setTimeout(r, millis));
+}
+
+/**
+ * let t = Date.now()
+ * sleep(100).then(() => console.log(Date.now() - t)) // 100
+ */