Add sponsorship section to README

Added sponsorship section with Cast AI details.

Author: samber

README.md

@@ -34,6 +34,15 @@
   <hr>
   <sup><b>Sponsored by:</b></sup>
   <br>
+  <a href="https://cast.ai/samuel">
+    <div>
+      <img src="https://github.com/user-attachments/assets/502f8fa8-e7e8-4754-a51f-036d0443e694" width="200" alt="Cast AI">
+    </div>
+    <div>
+      Run Kubernetes on autopilot – faster, smarter, cost-optimized.
+    </div>
+  </a>
+  <br>
   <a href="https://www.dash0.com?utm_campaign=148395251-samber%20github%20sponsorship&utm_source=github&utm_medium=sponsorship&utm_content=samber">
     <div>
       <img src="https://github.com/user-attachments/assets/b1f2e876-0954-4dc3-824d-935d29ba8f3f" width="200" alt="Dash0">