docs: add buy me a coke

README.md

@@ -231,6 +231,12 @@ yarn deploy
   <a href="https://github.com/zaunist/zmail">
     <img src="https://img.shields.io/github/stars/zaunist/zmail?style=social" alt="GitHub stars" />
   </a>
+  
+  <p style="margin-top: 15px;">
+    <a href="https://tiny-bush-0bef.realyourdad.workers.dev/" target="_blank">
+      <img src="https://img.shields.io/badge/Buy_Me_A_Coke-FF5E5B?style=for-the-badge&logo=coca-cola&logoColor=white" alt="Buy Me A Coke" width="200" style="border-radius: 8px;" height="51" />
+    </a>
+  </p>
 </div>
 
 ## 📄 许可证