Create a filter carousel item

Each filter item in the carousel displays a
circular image with a color applied to the image
that corresponds to the associated filter color.

Define a new stateless widget called FilterItem
that displays a single list item.

Implement the filter carousel

Filter items scroll to the left and right as the user drags. Scrolling requires 
some kind of Scrollable widget.

You might consider using a horizontal ListView widget,
but a ListView widget positions the first element at the
beginning of the available space, not at 
the center, where your selector ring sits.

A PageView widget is better suited for a carousel.
A PageView widget lays out its children from the
center of the available space and provides snapping physics.
Snapping physics is what causes an item to snap to the center, 
no matter where the user releases a drag.

Scrollable widget with a

viewportBuilder, and place a