Pull in the header for clamp

When doing a build with my own build of clang-20 on an Ubuntu 22.04
system I got a build failure due to this.

Author: alycm

Utilities/include/image_conv.h

@@ -9,6 +9,8 @@
 #ifndef __IMAGE_CONV_H__
 #define __IMAGE_CONV_H__
 
+#include <algorithm> // For clamp
+
 #define STB_IMAGE_IMPLEMENTATION
 #include <stb_image.h>
 #define STB_IMAGE_WRITE_IMPLEMENTATION