[Core] Add case-insensitive String::containsn

editor/plugins/script_editor_plugin.cpp

@@ -374,7 +374,7 @@ void ScriptEditorQuickOpen::_update_search() {
 
 	for (int i = 0; i < functions.size(); i++) {
 		String file = functions[i];
-		if ((search_box->get_text().is_empty() || file.findn(search_box->get_text()) != -1)) {
+		if ((search_box->get_text().is_empty() || file.containsn(search_box->get_text()))) {
 			TreeItem *ti = search_options->create_item(root);
 			ti->set_text(0, file);
 			if (root->get_first_child() == ti) {