Add onChange callback to `SplitterElement`

[eskimoblood]

Is your feature request related to a problem?

We use the Splitter Layout where some columns can be turn off and on again. As we also use initial sizes every toggle will rerender the columns with there initial size. Right now there is no build in way to get the size of the columns after they were changed

Describe the solution you'd like

We would like to get notified about the updated size by passing an callback that returns the new column width after the change

onSizeChange: (w:number) => void

Describe alternatives you've considered

No response

Additional Context

No response

Organization

SAP Signavio

Declaration

• I’m not disclosing any internal or sensitive information.