SDL_mixer: SDL_mixer.h: Added a link to SDL_PropertiesID documentation.

From d80acf522e24a3d858cfdcbd94ab58056a57a94b Mon Sep 17 00:00:00 2001
From: "Ryan C. Gordon" <[EMAIL REDACTED]>
Date: Mon, 22 Dec 2025 00:29:33 -0500
Subject: [PATCH] SDL_mixer.h: Added a link to SDL_PropertiesID documentation.

Fixes #780.
---
 include/SDL3_mixer/SDL_mixer.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/SDL3_mixer/SDL_mixer.h b/include/SDL3_mixer/SDL_mixer.h
index 69dd2da4..cfb3604e 100644
--- a/include/SDL3_mixer/SDL_mixer.h
+++ b/include/SDL3_mixer/SDL_mixer.h
@@ -613,6 +613,8 @@ extern SDL_DECLSPEC MIX_Audio * SDLCALL MIX_LoadAudio(MIX_Mixer *mixer, const ch
  * LoadAudio functions do. This function uses properties to dictate how it
  * operates, and exposes functionality the other functions don't provide.
  *
+ * SDL_PropertiesID are discussed in [SDL's documentation](https://wiki.libsdl.org/SDL3/CategoryProperties).
+ *
  * These are the supported properties:
  *
  * - `MIX_PROP_AUDIO_LOAD_IOSTREAM_POINTER`: a pointer to an SDL_IOStream to
@@ -1620,6 +1622,8 @@ extern SDL_DECLSPEC Sint64 SDLCALL MIX_FramesToMS(int sample_rate, Sint64 frames
  * defaults, and specifying a 0 for `options` will choose defaults for
  * everything.
  *
+ * SDL_PropertiesID are discussed in [SDL's documentation](https://wiki.libsdl.org/SDL3/CategoryProperties).
+ *
  * These are the supported properties:
  *
  * - `MIX_PROP_PLAY_LOOPS_NUMBER`: The number of times to loop the track when
@@ -2922,6 +2926,8 @@ typedef struct MIX_AudioDecoder MIX_AudioDecoder;
  * etc. In most cases, the caller should pass a zero to specify no extra
  * properties.
  *
+ * SDL_PropertiesID are discussed in [SDL's documentation](https://wiki.libsdl.org/SDL3/CategoryProperties).
+ *
  * When done with the audio decoder, it can be destroyed with
  * MIX_DestroyAudioDecoder().
  *