Add class names support

[yanalshoubaki]

Is your feature request related to a problem? Please describe.
When i want to edit style for tree, i can't add class names for style module, the current solution only with styled components we can override it.

Describe the solution you'd like
Add props className so we can add classNames for the components

[kiran-pillai]

Lack of support for this also means that we cannot control the width of flex container, in the case that we want the chart to be a fixed width @daniel-hauser

[Boris-Scharinger]

that would be awesome, full support!