docs: Update README "Help wanted"

Co-authored-by: Copilot <copilot@github.com>

Author: lxsaah

README.md

@@ -20,6 +20,9 @@
 <a href="LICENSE" target="_blank">
     <img src="https://img.shields.io/badge/license-Apache%202.0-blue.svg" alt="License">
 </a>
+<a href="https://buttondown.com/aimdb" target="_blank">
+    <img src="https://img.shields.io/badge/newsletter-subscribe-1adbc8.svg" alt="Newsletter">
+</a>
 </p>
 
 AimDB turns data contracts into the architecture. Define your schemas once and deploy them unchanged across microcontrollers, edge gateways, Kubernetes and the browser, with explicit, typed migrations when the contract evolves.
@@ -252,5 +255,5 @@ See the [contributing guide](CONTRIBUTING.md) for build, test and style requirem
 <p align="center">
   <strong>Distributed by design. Data-driven by default.</strong>
   <br><br>
-  <a href="https://aimdb.dev/docs/getting-started">Get started</a> · <a href="https://aimdb.dev">Live demo</a> · <a href="https://github.com/aimdb-dev/aimdb/discussions">Join the discussion</a> · <a href="https://buttondown.com/aimdb"><img src="https://img.shields.io/badge/newsletter-subscribe-1adbc8?style=flat-square" alt="Newsletter"></a>
+  <a href="https://aimdb.dev/docs/getting-started">Get started</a> · <a href="https://aimdb.dev">Live demo</a> · <a href="https://github.com/aimdb-dev/aimdb/discussions">Join the discussion</a>
 </p>