[nostalgia/core/gba] Add user input support

src/nostalgia/core/sdl/core.cpp

@@ -9,6 +9,7 @@
 #include <SDL.h>
 
 #include <nostalgia/core/gfx.hpp>
+#include <nostalgia/core/input.hpp>
 #include <nostalgia/core/core.hpp>
 
 namespace nostalgia::core {
@@ -52,4 +53,8 @@ uint64_t ticksMs() {
 	return SDL_GetTicks();;
 }
 
+bool buttonDown(Key) {
+	return false;
+}
+
 }