docs: add StarletteAdminPlugin to admin plugins list (#9)

Author: noamsto

README.md

@@ -131,6 +131,7 @@ that you would normally find as third-party extensions in other frameworks.
 - [Piccolo Admin](https://github.com/piccolo-orm/piccolo_admin) - A powerful and modern admin GUI, using the Piccolo
   ORM.
 - [SQLAdminPlugin](https://github.com/peterschutt/sqladmin-litestar-plugin) - Integrates SQLAdmin with a Litestar application.
+- [StarletteAdminPlugin](https://github.com/noamsto/starlette-admin-litestar-plugin) - Integrates Starlette Admin with a Litestar application.
 
 ### Auth