Support forced Y coordinate drag motion

[dboundz]

In many UX cases you only want to user to be able to drag it item veritically, or horizontally but not both at the same time (as with a Kanban).

Other framework DnD libraries I've used in the past support the ability to restrict the drag animation to just up / down or left / right but I don't believe that's baked in to this.

Would be a great enhancement as it's a good UX when needed.

[isaacHagoel]

I think someone tried to implement this in the past and it proved to be non-trivial.
I am open to PRs. If you want to give it a go I can assist.
Otherwise, I might get to this but not sure exactly when.