Improve README

bindings/c/examples/sdl/README.md

@@ -8,10 +8,10 @@ The process will vary based on your operating system.
 
 ### On Windows:
 
-First download a copy of SDL2 and extract it.
+First download an SDL2 development package from the project's [GitHub release page](https://github.com/libsdl-org/SDL/releases) (SDL2-devel-2.x.y-VC.zip for MSVC) and extract it.
 
 ```bash
-cmake -S . -B build -DACCESSKIT_DIR="../.." -DSDL2_ROOT="<PATH_TO_SDL2_INSTALLATION>/cmake"
+cmake -S . -B build -DACCESSKIT_DIR="../.." -DSDL2_DIR="<PATH_TO_SDL2_PACKAGE>/cmake"
 cmake --build build --config Release
 ```
 
@@ -25,3 +25,12 @@ Make sure to install SDL2 and its development package.
 cmake -S . -B build -DACCESSKIT_DIR="../.." -DCMAKE_BUILD_TYPE=Release
 cmake --build build
 ```
+
+### On Mac OS X
+
+First download an SDL2 package from the project's [GitHub release page](https://github.com/libsdl-org/SDL/releases) (SDL2-2.x.y.dmg) and copy `SDL2.framework` to `/Library/Frameworks`.
+
+```bash
+cmake -S . -B build -DACCESSKIT_DIR="../.." -DCMAKE_BUILD_TYPE=Release
+cmake --build build
+```