LibGUI: Include keyboard modifier state with button on_click calls

This will allow you us to implement special behavior when Ctrl+clicking
a button.

DevTools/HackStudio/FindInFilesWidget.cpp

@@ -153,7 +153,7 @@ FindInFilesWidget::FindInFilesWidget()
         current_editor().set_focus(true);
     };
 
-    m_button->on_click = [this] {
+    m_button->on_click = [this](auto) {
         auto results_model = find_in_files(m_textbox->text());
         m_result_view->set_model(results_model);
     };