SDL_mixer: Update INTRO-visualstudio.md

From 8fa0c24c5c393fc3ad9523fbe9baa454c85713d3 Mon Sep 17 00:00:00 2001
From: Tyler Winters <[EMAIL REDACTED]>
Date: Sat, 25 Apr 2026 05:20:52 -0600
Subject: [PATCH] Update INTRO-visualstudio.md

Copied missing step from SDL_ttf instructions.
---
 docs/INTRO-visualstudio.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/INTRO-visualstudio.md b/docs/INTRO-visualstudio.md
index 267d81b8..c794650f 100644
--- a/docs/INTRO-visualstudio.md
+++ b/docs/INTRO-visualstudio.md
@@ -3,6 +3,8 @@
 
 The easiest way to use SDL_mixer is to include it along with SDL as subprojects in your project.
 
+First, make sure you have downloaded the external dependencies. You can do that by running Get-GitModules.ps1 in the external directory.
+
 We'll start by creating a simple project to build and run [hello.c](hello.c)
 
 - Create a new project in Visual Studio, using the C++ Empty Project template