Add cutscene test menu

This allows translators to test all text boxes in the scripts. It
doesn't run the scripts themselves - it only shows the basic appearance
of each text box individually, so context may be lost but it's good to
have a way to see any text boxes that might otherwise not be easily
seen because they require specific circumstances to appear.

desktop_version/src/Localization.cpp

@@ -21,6 +21,7 @@ std::vector<LangMeta> languagelist;
 int languagelist_curlang;
 bool show_translator_menu = false;
 size_t limitscheck_current_overflow;
+std::vector<std::string> testable_script_ids;
 
 int n_untranslated_roomnames = 0;
 int n_unexplained_roomnames = 0;