message: Add mobile styles for package manager selector
diff: +@import "_variables";
  +@import "_mixins";
  +
  ul.package-manager-selector {
  display: flex;
  padding: 0;
  @@ -8,6 +11,12 @@ ul.package-manager-selector {
  background-color: var(--container-color);
  border-bottom: none;
  + @include mobile-only {
  + border-radius: 0;
  + margin: 0 -20px;
  + padding: 0 10px;
  + }
  +
  li {
  padding: 10px;
  list-style: none;
  