Add menu roles for better mac menus

Adding "menuRole" properties to standard menu actions (About,
Preferences, Quit) lets Qt move them to their standard place in the
macOS menu bar (without having to rely on their text content, which
breaks when localizing). This also automatically sets the "Preferences"
shortcut to the standard "Cmd+," instead of "Cmd+P".

This should have no impact on other platforms.

See https://doc.qt.io/qt-6/qmenubar.html#qmenubar-as-a-global-menu-bar

src/main/python/main/ayab/menu_gui.ui

@@ -65,6 +65,9 @@
    <property name="shortcut">
     <string notr="true">Ctrl+Q</string>
    </property>
+   <property name="menuRole">
+    <enum>QAction::QuitRole</enum>
+   </property>
   </action>
   <action name="action_load_AYAB_firmware">
    <property name="text">
@@ -96,6 +99,9 @@
    <property name="text">
     <string>Help – About</string>
    </property>
+   <property name="menuRole">
+    <enum>QAction::AboutRole</enum>
+   </property>
   </action>
   <action name="action_help">
    <property name="text">
@@ -189,6 +195,9 @@
    <property name="shortcut">
     <string notr="true">Ctrl+P</string>
    </property>
+   <property name="menuRole">
+    <enum>QAction::PreferencesRole</enum>
+   </property>
   </action>
  </widget>
  <resources/>