Spreadsheet: Improve 'Functions Help' button

Add icon and tooltip to 'Functions Help' button.

Userland/Applications/Spreadsheet/SpreadsheetWidget.cpp

@@ -43,7 +43,9 @@ SpreadsheetWidget::SpreadsheetWidget(GUI::Window& parent_window, NonnullRefPtrVe
     auto& current_cell_label = top_bar.add<GUI::Label>("");
     current_cell_label.set_fixed_width(50);
 
-    auto& help_button = top_bar.add<GUI::Button>("i");
+    auto& help_button = top_bar.add<GUI::Button>("");
+    help_button.set_icon(Gfx::Bitmap::try_load_from_file("/res/icons/16x16/app-help.png").release_value_but_fixme_should_propagate_errors());
+    help_button.set_tooltip("Functions Help");
     help_button.set_fixed_size(20, 20);
     help_button.on_click = [&](auto) {
         if (!m_selected_view) {