SDL_image: Document the animation delay units

SDL Commits
1 
From a8d223f9ead4639cf07ad2612bfe883a2a6093b8 Mon Sep 17 00:00:00 2001
From: Sam Lantinga <[EMAIL REDACTED]>
Date: Tue, 22 Apr 2025 10:40:00 -0700
Subject: [PATCH] Document the animation delay units

Fixes https://github.com/libsdl-org/SDL_image/issues/550
---
 include/SDL3_image/SDL_image.h | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/include/SDL3_image/SDL_image.h b/include/SDL3_image/SDL_image.h
index b362bba9..bde984db 100644
--- a/include/SDL3_image/SDL_image.h
+++ b/include/SDL3_image/SDL_image.h
@@ -1974,10 +1974,11 @@ extern SDL_DECLSPEC bool SDLCALL IMG_SaveJPG_IO(SDL_Surface *surface, SDL_IOStre
  */
 typedef struct IMG_Animation
 {
-	int w, h;
-	int count;
-	SDL_Surface **frames;
-	int *delays;
+    int w;                  /**< The width of the frames */
+    int h;                  /**< The height of the frames */
+    int count;              /**< The number of frames */
+    SDL_Surface **frames;   /**< An array of frames */
+    int *delays;            /**< An array of frame delays, in milliseconds */
 } IMG_Animation;
 
 /**