chore: adds YouTube channel badge

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nunomaduro

README.md

@@ -1,3 +1,7 @@
+<p align="center">
+    <a href="https://youtube.com/@nunomaduro?sub_confirmation=1"><img alt="YouTube Channel Subscribers" src="https://img.shields.io/youtube/channel/subscribers/UCO_hYZF2gb_CyG5sA7ArlGg?style=flat&label=youtube&color=brightgreen"></a>
+</p>
+
 This repository contains the Pest 1 Plugin Global Assertions, and it's now deprecated.
 
 > If you want to start testing your application with Pest, visit the main **[Pest Repository](https://github.com/pestphp/pest)**.