Update README.md

Author: cameroncooke

README.md

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 A Model Context Protocol (MCP) server that provides Xcode-related tools for integration with AI assistants and other MCP clients.
 
 [![CI](https://github.com/cameroncooke/XcodeBuildMCP/actions/workflows/ci.yml/badge.svg)](https://github.com/cameroncooke/XcodeBuildMCP/actions/workflows/ci.yml) [![CodeQL](https://github.com/cameroncooke/XcodeBuildMCP/actions/workflows/github-code-scanning/codeql/badge.svg)](https://github.com/cameroncooke/XcodeBuildMCP/actions/workflows/github-code-scanning/codeql)
+[![Licence: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 
 ## Table of contents