Add DeepWiki badge to README

Added a badge link to DeepWiki in the README.

Author: Anmol1696

README.md

@@ -9,6 +9,7 @@
     <img height="20" src="https://github.com/constructive-io/constructive/actions/workflows/run-tests.yaml/badge.svg" />
   </a>
    <a href="https://github.com/constructive-io/constructive/blob/main/LICENSE"><img height="20" src="https://img.shields.io/badge/license-MIT-blue.svg"/></a>
+   <a href="https://deepwiki.com/constructive-io/constructive"><img height="20" src="https://deepwiki.com/badge.svg"/></a>
 </p>
 
 **Constructive** is a complete ecosystem for modular PostgreSQL development. Design your database schema, manage it with our package manager, and get a production-ready GraphQL API automatically. Build composable database modules, version them like npm packages, and deploy with confidence.