Add 'getting started' extensions documentation (#9536)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

packages/cli/src/commands/extensions/examples/mcp-server/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "mcp-server-example",
+  "version": "1.0.0",
+  "description": "Example MCP Server for Gemini CLI Extension",
+  "type": "module",
+  "main": "example.js",
+  "scripts": {
+    "build": "tsc"
+  },
+  "devDependencies": {
+    "typescript": "~5.4.5",
+    "@types/node": "^20.11.25"
+  },
+  "dependencies": {
+    "@modelcontextprotocol/sdk": "^1.11.0",
+    "zod": "^3.22.4"
+  }
+}