hints: Add "metal" to the list of SDL_RENDER_DRIVER hints.
diff --git a/include/SDL_hints.h b/include/SDL_hints.h
index 05e0cbe..7184b3d 100644
--- a/include/SDL_hints.h
+++ b/include/SDL_hints.h
@@ -76,6 +76,7 @@ extern "C" {
* "opengl"
* "opengles2"
* "opengles"
+ * "metal"
* "software"
*
* The default varies by platform, but it's the first one in the list that