docs: update menu item '&' escaping (#27817)

Co-authored-by: mlaurencin <mlaurencin@electronjs.org>

docs/api/menu.md

@@ -22,8 +22,10 @@ Sets `menu` as the application menu on macOS. On Windows and Linux, the
 Also on Windows and Linux, you can use a `&` in the top-level item name to
 indicate which letter should get a generated accelerator. For example, using
 `&File` for the file menu would result in a generated `Alt-F` accelerator that
-opens the associated menu. The indicated character in the button label gets an
-underline. The `&` character is not displayed on the button label.
+opens the associated menu. The indicated character in the button label then gets an
+underline, and the `&` character is not displayed on the button label.
+
+In order to escape the `&` character in an item name, add a proceeding `&`. For example, `&&File` would result in `&File` displayed on the button label.
 
 Passing `null` will suppress the default menu. On Windows and Linux,
 this has the additional effect of removing the menu bar from the window.