Set the pad lights on the PS5 controller corresponding to the player index

Also allow setting the player index from testgamecontroller using the number keys

test/testgamecontroller.c

@@ -303,6 +303,14 @@ loop(void *arg)
             break;
 
         case SDL_KEYDOWN:
+            if (event.key.keysym.sym >= SDLK_0 && event.key.keysym.sym <= SDLK_9) {
+                if (gamecontroller) {
+                    int player_index = (event.key.keysym.sym - SDLK_0);
+
+                    SDL_GameControllerSetPlayerIndex(gamecontroller, player_index);
+                }
+                break;
+            }
             if (event.key.keysym.sym != SDLK_ESCAPE) {
                 break;
             }