docs: add gitcgr code graph badge (#578)

Author: Vitali Avagyan

README.md

@@ -1,5 +1,7 @@
 # CodexMonitor
 
+[![gitcgr](https://gitcgr.com/badge/Dimillian/CodexMonitor.svg)](https://gitcgr.com/Dimillian/CodexMonitor)
+
 ![CodexMonitor](screenshot.png)
 
 CodexMonitor is a Tauri app for orchestrating multiple Codex agents across local workspaces. It provides a sidebar to manage projects, a home screen for quick actions, and a conversation view backed by the Codex app-server protocol.