Tooltip如何设置柱线图的tooltipMarkerStyle

柱状图和折线图一同显示的时候，如官方示例： https://antv-f2.gitee.io/zh/examples/component/legend#custom
柱状图的背景 tooltipMarker 就不见了，如何将它显示出来？

Start with the official custom-legend example linked in the issue and reproduce the case where a bar chart and line chart are shown together. Investigate how the tooltip marker is rendered in that example; done means the bar chart's background tooltipMarker is visible and its style can be configured as requested.

Written by the indexing model from the issue text.