Refactored inventory some so that the UI is not so knowing of the internals.

inventory.hpp

@@ -1,6 +1,7 @@
 #pragma once
 #include "components.hpp"
 #include <nlohmann/json.hpp>
+#include "levelmanager.hpp"
 
 namespace components {
   using namespace nlohmann;
@@ -26,5 +27,7 @@ namespace components {
     int item_index(std::string id);
 
     void erase_item(size_t at);
+
+    std::pair<bool, std::string> use(GameLevel &level, size_t at);
   };
 }