docs: add Codex MCP configuration guide (#95)

Co-authored-by: Sebastian Benz <sbenz@google.com>

Author: kingsword09

README.md

@@ -66,6 +66,17 @@ claude mcp add chrome-devtools npx chrome-devtools-mcp@latest
   Follow https://docs.cline.bot/mcp/configuring-mcp-servers and use the config provided above.
 </details>
 
+<details>
+  <summary>Codex</summary>
+  Follow the <a href="https://github.com/openai/codex/blob/main/docs/advanced.md#model-context-protocol-mcp">configure MCP guide</a>
+  using the standard config from above. You can also install the Chrome DevTools MCP server using the Codex CLI:
+
+```bash
+codex mcp add chrome-devtools -- npx chrome-devtools-mcp@latest
+```
+
+</details>
+
 <details>
   <summary>Copilot / VS Code</summary>
   Follow the MCP install <a href="https://code.visualstudio.com/docs/copilot/chat/mcp-servers#_add-an-mcp-server">guide</a>,