Make ContinuousLinearScale display_decimals a parameter

[lioPixiumDigital]

It's be awesome to be able to set the number of decimals.

right now I'm using an ugly hack:

      custom_value_scale: Contex.ContinuousLinearScale.new()
        |> Contex.ContinuousLinearScale.domain(0, max_display)
        |> Contex.ContinuousLinearScale.interval_count(10)
        |> Map.merge(%{display_decimals: 0}) # ugly hack

[mindok]

So the official way of doing this would be through the :custom_tick_formatter options on each of the appropriate plots, but it would make sense to expose this for a ContinuousLinearScale and something similar for time scales