Enhancement: Support dragging items between Calcite Value Lists

[Csmith246]

Description

Support the ability to drag a Calcite Value List Item from one Calcite Value List to a different Calcite Value List.

Acceptance Criteria

• List Item can be dragged between different lists.
• Make that cross list movement accessible.
• Expose helpful event hooks for the move operation.

Relevant Info

We have already implemented this by using private properties on the Calcite Value List. This implementation can be viewed here. The way to implement the cross list dragging is to give two Calcite Value Lists the same group name. So maybe it would be helpful to expose that group name as an input property on the Calcite Value List? The SortableJS events that were used in our implementation were onAdd and onRemove. So, I would say, consider exposing these (and maybe other) events, so that developers can have hooks to use to support any in app behavior that happens from a cross list drag.

Which Component

Calcite Value List, and Calcite Value List Item

Example Use Case

We are using the Calcite Value List to create a widget that allows users to position and order map widgets on the mapView ui. Our implementation can be viewed here

[driskull]

I can help with this as need be. We probably don't want to expose the Sortable instance at all incase we change libraries in the future.

[jcfranco]

#1006 may have an impact on this.

[jcfranco]

Addressed by #1059.