improve INTRO-visualstudio.md with more detailed Visual Studio steps

Thanks @Atkclf!

(cherry picked from commit cf7c652)

Author: slouken

docs/INTRO-visualstudio.md

@@ -11,6 +11,8 @@ We'll start by creating a simple project to build and run [hello.c](hello.c)
 - Add hello.c to the Source Files
 - Right click the solution, select add an existing project, navigate to the SDL VisualC/SDL directory and add SDL.vcxproj
 - Right click the solution, select add an existing project, navigate to the SDL_ttf VisualC directory and add SDL_ttf.vcxproj
+- Select your SDL_ttf project and go to Project -> Add Reference and select SDL3
+- Select your SDL_ttf project and go to Project -> Properties, set the filter at the top to "All Configurations" and "All Platforms", select VC++ Directories and modify the default SDL path in "Include Directories" to point to your SDL include directories
 - Select your main project and go to Project -> Add Reference and select SDL3 and SDL3_ttf
 - Select your main project and go to Project -> Properties, set the filter at the top to "All Configurations" and "All Platforms", select VC++ Directories and add the SDL and SDL_ttf include directories to "Include Directories"
 - Build and run!