docs: add Grok Build CLI configuration section (#2294)

# Summary

adds Grok Build CLI to the MCP client configuration list in README.md

# Verification

Verified visually + git diff

README.md

@@ -333,6 +333,16 @@ Alternatively, follow the <a href="https://github.com/google-gemini/gemini-cli/b
   using the standard config from above.
 </details>
 
+<details>
+  <summary>Grok Build CLI</summary>
+
+```bash
+grok mcp add chrome-devtools npx chrome-devtools-mcp@latest
+```
+
+See the <a href="https://docs.x.ai/build/features/skills-plugins-marketplaces">docs</a> for more options
+</details>
+
 <details>
   <summary>JetBrains AI Assistant & Junie</summary>