Use the formatter function of the Apache ECharts tooltp in the ods-charts tooltipSuggest a new feature

[jacques-lebourgeois]

Prerequisites

• I have searched for duplicate or closed feature requests
• I have read the contributing guidelines

Proposal

Aautomatically use the Apache Echarts tooltip formatter function when provided combined with the ods-charts tooltip.

Motivation and context

If you want to add a unit in the Apache ECharts tooltip, you have to use the formatter function of the tooltip. Here's an example of the unit added in the Apache ECharts tooltip (without ods-charts tooltip) : https://codepen.io/jacques-lebourgeois/pen/mdgKQBx.

If you use tooltips charted by ods-charts, unfortunately our library is incompatible with the use of the tooltip's formatter function and you can't both use the ods-charts tooltips and unit added in the formatter function.
You have to specify a different funtion to add unit like demonstrated in https://codepen.io/jacques-lebourgeois/pen/NWmzEVQ

The evolution is to re-use the Apache ECharts tooltip formatter() function when provided