Ngx-charts: Send index to formatting functions

[antoniogenaro]

Is your feature request related to a problem? Please describe.
In formatting functions (labelFormatting, xAxisTickFormatting, yAxisTickFormatting) only the text is sending, and you can't use value or any other data to format

Describe the solution you'd like
Adding a second param with the index would be nice to get the rest of data that you need

[hilel]

Would like to have it too, thanks