docs: update CLI command for adding GitHub PAT in README

Author: RossTarrant

README.md

@@ -212,7 +212,7 @@ To keep your GitHub PAT secure and reusable across different MCP hosts:
 
    ```bash
    # CLI usage
-   claude mcp update github -e GITHUB_PERSONAL_ACCESS_TOKEN=$GITHUB_PAT
+   claude mcp add github -e GITHUB_PERSONAL_ACCESS_TOKEN=$GITHUB_PAT -- docker run -i --rm -e GITHUB_PERSONAL_ACCESS_TOKEN ghcr.io/github/github-mcp-server
 
    # In config files (where supported)
    "env": {