message: feat(Cell): change dragging background
diff: }
  .Cell--dragging {
  - background-color: var(--vkui--color_background_modal);
  + background-color: var(--vkui--color_background_secondary);
  box-shadow: var(--vkui--elevation3);
  - opacity: 0.8;
  z-index: var(--vkui_internal--z_index_cell_dragging);
  }
  