Update readme.md

Author: H2xDev

readme.md

@@ -31,6 +31,7 @@ Or for those who just want to port their map from Source Engine to Godot and see
 ## Installation and Usage
 - [Installation Guide](https://github.com/H2xDev/GodotVMF/wiki/Installation-guide)
 - [Documentation](https://github.com/H2xDev/GodotVMF/wiki)
+- [Materials Video Tutorial](https://www.youtube.com/watch?v=6anSX-sWgW0)
 
 ## Video demonstration
 [![Click to open Youtube video](https://github.com/user-attachments/assets/d9b421e6-69c0-499e-8ccf-0390ddb1f548)](https://www.youtube.com/watch?v=5XYfvbIAlJU)