update keyboard shortcuts

src/ui/BuildButtonGrid.cpp

@@ -130,3 +130,20 @@ void BuildButtonGrid::handleEvent(std::shared_ptr<const DemolishModeChangedEvent
 {
     m_demolishButton->setChecked(event->active);
 }
+
+void BuildButtonGrid::handleEvent(std::shared_ptr<const BuildHotkeyPressedEvent> event)
+{
+    for (std::size_t i = 0; i < m_types.size(); ++i)
+    {
+        if (m_types[i] == event->type)
+        {
+            // Equivalent to clicking the build button: a disabled (unaffordable)
+            // button cannot be clicked, so the hotkey is likewise inert.
+            if (m_buttons[i]->isEnabled())
+            {
+                onBuildButton(static_cast<int>(i));
+            }
+            return;
+        }
+    }
+}