SDL: Fixed compatibility with sdl2-compat (thanks @sezero!)

From 30a2291d594a1ccb0b67e2bff2d805c531d2f47f Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Mon, 20 Nov 2023 08:46:12 -0800
Subject: [PATCH] Fixed compatibility with sdl2-compat (thanks @sezero!)

---
 include/SDL3/SDL_pixels.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/SDL3/SDL_pixels.h b/include/SDL3/SDL_pixels.h
index 02bae04101e7..3d39e2e98259 100644
--- a/include/SDL3/SDL_pixels.h
+++ b/include/SDL3/SDL_pixels.h
@@ -88,7 +88,6 @@ typedef enum
 {
     SDL_PIXELTYPE_UNKNOWN,
     SDL_PIXELTYPE_INDEX1,
-    SDL_PIXELTYPE_INDEX2,
     SDL_PIXELTYPE_INDEX4,
     SDL_PIXELTYPE_INDEX8,
     SDL_PIXELTYPE_PACKED8,
@@ -98,7 +97,9 @@ typedef enum
     SDL_PIXELTYPE_ARRAYU16,
     SDL_PIXELTYPE_ARRAYU32,
     SDL_PIXELTYPE_ARRAYF16,
-    SDL_PIXELTYPE_ARRAYF32
+    SDL_PIXELTYPE_ARRAYF32,
+    /* appended at the end for compatibility with sdl2-compat:  */
+    SDL_PIXELTYPE_INDEX2
 } SDL_PixelType;
 
 /** Bitmap pixel order, high bit -> low bit. */