Fix text rendering issue in the menu bar

To denote the hotkey assigned with each menu item an ampersand is used
in the configuration. This ampersand was previously rendered directly
to the screen due to the `UM.Label`. This is now correctly replaced by
an underline.

CURA-8688

resources/qml/MainWindow/ApplicationMenu.qml

@@ -32,7 +32,10 @@ Item
 
             contentItem: UM.Label
             {
-                text: menuBarItem.text
+                text: menuBarItem.text.replace(new RegExp("&([A-Za-z])"), function (match, character)
+                {
+                    return `<u>${character}</u>`;
+                })
                 horizontalAlignment: Text.AlignLeft
                 verticalAlignment: Text.AlignVCenter
             }