Added SDL_SCALEMODE_PIXELART

This is based on the algorithm presented by t3ssel8r:
https://www.youtube.com/watch?v=d6tp43wZqps

include/SDL3/SDL_surface.h

@@ -83,8 +83,9 @@ typedef Uint32 SDL_SurfaceFlags;
 typedef enum SDL_ScaleMode
 {
     SDL_SCALEMODE_INVALID = -1,
-    SDL_SCALEMODE_NEAREST, /**< nearest pixel sampling */
-    SDL_SCALEMODE_LINEAR   /**< linear filtering */
+    SDL_SCALEMODE_NEAREST,  /**< nearest pixel sampling */
+    SDL_SCALEMODE_LINEAR,   /**< linear filtering */
+    SDL_SCALEMODE_PIXELART  /**< nearest pixel sampling with improved scaling for pixel art */
 } SDL_ScaleMode;
 
 /**