Allow option to clear color picker colors

[nickofthyme]

Is your feature request related to a problem? Please describe.
When using a custom color picker in the legend. The onChange callback does not allow for null value or any other way to clear the custom color selection.

Describe the solution you'd like
The onChange callback takes a null value to clear the selected color value.

Describe alternatives you've considered
Rerender entire chart to update color selection

[markov00]

🎉 This issue has been resolved in version 24.1.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

Your semantic-release bot 📦🚀