make fancy file picker function game-specific

src/scenedit/scen.core.cpp

@@ -3776,3 +3776,7 @@ void edit_custom_sounds() {
 		snd_names.swap(scenario.snd_names);
 	}
 }
+
+fs::path run_file_picker(bool saving){
+	return os_file_picker(saving);
+}