What problem does this feature solve?
When displaying data that shows power laws, one bar can often be much larger than others. In these cases, if would be helpful to allow the click target on the barchart to be the highlighted area on hover (see image below as an example) when onValueChange is specified.

What does the proposed API look like?
Add makeHoverAreaClickable as a boolean parameter for the <BarChart> component.
If set to true, the hover area is clickable and the same action is performed specified in onValueChange