message: Fix backdrop bug in PR review
  Fixes
diff: @@ -751,7 +751,7 @@ a.tabnav-extra[href$="mastering-markdown/"] {
  :root body.menu-active .modal-backdrop,
  :root .dropdown-details[open] > summary::before {
  background: rgba(0, 0, 0, 0.1);
  - z-index: 29;
  + z-index: 20; /* Don't mess with this value so easily */
  animation: fade-in 0.2s;
  }
  :root .pagehead ul.pagehead-actions {
  