Forward collectionView(_:contextMenuConfigurationForItemAt:point:) to one of the delegates

[FaizanDurrani]

Right now there's no way to add context menus to the items in the collection view, (see #176 (comment)) forwarding this UICollectionViewDelegate method to the scrollDelegate (or layoutDelegate? or even a new type of delegate) would allow consumers to set up context menus.

That being said, a more well rounded API would be to hook it up to the declarative syntax of items, similar to how didSelect works. Doing so, context menu configuration can be tied to the item in the section rather than being imperatively defined using itemPath(for:) in the delegate method.

[FaizanDurrani]

A correction to the original issue: There is a way to add context menus to the items by directly adding a UIContextMenuInteraction to the view, and then hooking up the configuration as a Behavior.

A more "Epoxy"-like API would be great though.