destroy tile atlas structure after it is not needed anymore

src/main.cpp

@@ -926,6 +926,7 @@ int main(int argc, char **argv) {
         }
         stbi_image_free(data);
     }
+    sma_atlas_destroy(tile_atlas);
 
     SDL_GPUTexture *tile_atlas_texture = create_shader_texture("tile_atlas", tile_atlas_texture_cpu, tile_atlas_size, tile_atlas_size, 4);
     free(tile_atlas_texture_cpu);