added Node 15 to compatibility table

Author: mtrezza

Diff for: README.md

@@ -111,6 +111,7 @@ Parse Server is continuously tested with the most recent releases of Node.js to
 | Node.js 10 | 10.23.2              | April 2021       | ✅ Fully compatible |
 | Node.js 12 | 12.20.1              | April 2022       | ✅ Fully compatible |
 | Node.js 14 | 14.15.4              | April 2023       | ✅ Fully compatible |
+| Node.js 15 | 15.8.0               | June 2021        | ✅ Fully compatible |
 
 #### MongoDB
 Parse Server is continuously tested with the most recent releases of MongoDB to ensure compatibility. We follow the [MongoDB support schedule](https://www.mongodb.com/support-policy) and only test against versions that are officially supported and have not reached their end-of-life date yet.