add npm version badge (#113)

* add npm version badge

* Update README.md

Author: ochafik

README.md

@@ -1,6 +1,6 @@
 # @modelcontextprotocol/ext-apps
 
-[![API Documentation](https://img.shields.io/badge/docs-API%20Reference-blue)](https://modelcontextprotocol.github.io/ext-apps/api/)
+[![npm version](https://img.shields.io/npm/v/@modelcontextprotocol/ext-apps.svg)](https://www.npmjs.com/package/@modelcontextprotocol/ext-apps) [![API Documentation](https://img.shields.io/badge/docs-API%20Reference-blue)](https://modelcontextprotocol.github.io/ext-apps/api/)
 
 This repo contains the SDK and [specification](https://github.com/modelcontextprotocol/ext-apps/blob/main/specification/draft/apps.mdx) for MCP Apps Extension ([SEP-1865](https://github.com/modelcontextprotocol/modelcontextprotocol/pull/1865)).