audio: add item pickup sound

Reviewed-on: NotAShelf/rogged#7
Co-authored-by: A.M. Rowsell <amr@frzn.dev>
Co-committed-by: A.M. Rowsell <amr@frzn.dev>

src/audio.c

@@ -95,6 +95,8 @@ void audio_play_attack(void) {
 void audio_play_item_pickup(void) {
   // High-pitched pickup sound
   play_tone(800.0f, 0.15f, 0.4f);
+  Sound pickup = LoadSound("./assets/sounds/itempickup.wav");
+  PlaySound(pickup);
 }
 
 void audio_play_enemy_death(void) {