Make renderer pointer const in load_asset_to_manager

include/AssetManager.h

@@ -35,7 +35,7 @@ AssetManager *create_asset_manager();
  * Returns the AssetID on success or an INVALID_ID in the case of failure.
  */
 AssetID load_asset_to_manager(AssetManager *am, const char *path,
-                              AssetType type, Renderer *renderer);
+                              AssetType type, const Renderer *renderer);
 
 /**
  * Removes an asset from the manager using its ID.