Docs: improvement around `dragging` property

[dgrcode]

What platform were you using when you found the bug?

any platform

Live code example

No response

Describe the Bug

Followup from https://github.com/xyflow/xyflow/issues/5211#issuecomment-2953701913

In some situations like copying, duplicating, or other manual node editing during dragging, the node's dragging property might get out of sync, which leads to unexpected selection behavior. @ha11owlemon found the right solution for this was manually setting dragging to false when the dragging stop (ref).

We could probably add a note on the onNodeDragStop docs mentioning this so user facing this issue easily understand how to fix the selection behavior.