message: style(TreeSelect): allow select text in content slot
diff: position: relative;
  display: flex;
  font-size: var(--van-tree-select-font-size);
  - user-select: none;
  &__nav {
  flex: 1;
  -webkit-overflow-scrolling: touch;
  &-item {
  + user-select: none;
  padding: var(--van-tree-select-nav-item-padding);
  }
  }
  padding: 0 32px 0 var(--van-padding-md);
  font-weight: var(--van-font-weight-bold);
  line-height: var(--van-tree-select-item-height);
  + user-select: none;
  cursor: pointer;
  &--active {
  