onClick change BarChartRodStackItem width

I want to change the `width` of a single `BarChartRodStackItem` when it is clicked. Initially, `BarChartRodStackItem` width is set by the `BarChartRodData` width. Changing the `BarChartRodData` width will change all of it's item width but I want to change the width of `BarChartRodStackItem` which is clicked. How do I achieve this?

Start by locating the BarChartRodStackItem and BarChartRodData definitions and tracing how a clicked item is represented in the Flutter bar chart. Reproduce the requested interaction in a small chart example; the work is done when one clicked stack item can have an independently changed width without changing the widths of its siblings.

Written by the indexing model from the issue text.