Update README.md

Author: arnaud-lb

README.md

@@ -14,6 +14,31 @@ The high level and low level *consumers*, *producer*, and *metadata* APIs are su
 
 Documentation is available [here](https://arnaud-lb.github.io/php-rdkafka/phpdoc/book.rdkafka.html).
 
+## Sponsors
+
+<table width="100%">
+<tr>
+<td>
+  <img width="1000" height="0">
+  <a href="https://upstash.com/?utm_source=php-rdkafka" >
+  <img src="https://raw.githubusercontent.com/upstash/sponsorship/master/kafka.png" alt="Upstash" width="260" align="right">
+  </a>
+
+<h3>Upstash: Serverless Kafka</h3>
+
+  <ul>
+    <li>True Serverless Kafka with per-request-pricing</li>
+    <li>Managed Apache Kafka, works with all Kafka clients</li>
+    <li>Built-in REST API designed for serverless and edge functions</li>
+  </ul>
+
+[Start for free in 30 seconds!](https://upstash.com/?utm_source=YOUR_PROJECT)
+</td>
+</tr>
+</table>
+
+php-rdkafka supports Ukraine. Proceeds from our generous sponsors are currently donated to the [Support Ukraine collective](https://opencollective.com/support-ukraine).
+
 ## Table of Contents
 
 1. [Installation](#installation)