Enlarge shift signup submission button

includes/view/ShiftEntry_view.php

@@ -139,7 +139,7 @@ function ShiftEntry_create_view_user($shift, Room $room, $angeltype, $comment)
             info(sprintf(__('Do you want to sign up for this shift as %s?'), AngelType_name_render($angeltype)), true),
             form([
                 //form_textarea('comment', __('Comment (for your eyes only):'), $comment),
-                form_submit('submit', icon('check-lg') . __('Save'))
+                form_element(null, form_submit('submit', icon('check-lg') . __('Save'), 'btn-lg', false), '', 'd-grid'),
             ])
         ]);
 }