Tooltip Synchronization between multiple graphs

* **C3 version**: 0.4.10 or 0.7.0 (Tried with both versions)
* **D3 version**:5.15.0
* **Browser**:chrome
* **OS**:Mac
Trying to plot multiple graph using c3 and have a synchronized tooltip on all the graphs. I have been referred this post: https://github.com/c3js/c3/issues/467. I couldn't find anything related or more similar to synchronizing tooltip. So I go ahead and figure out the workaround to customize the tooltip. This tooltip synchronization works perfectly for spline graphs and doesn't work with timeseries graph.

Spline type C3 - working as my expectation:
codepen link: [spline graph
](https://codepen.io/nagarajan_ceg/pen/XWbaPJV)

Timeseries type C3- Doesn't work as above:
codepen link: [Timeseries graph](https://codepen.io/nagarajan_ceg/pen/vYOJzOM)

I am not pretty sure about the whether this is a proper way of tooltip synchronization. It would be very grateful if it's possible to identify why it's happening properly at spline and not happening at timeseries one. Please let me know if there are any alternative better ideas to do this. I would like to appreciate any help on this.