Add tip for keyboard reordering (relations)

Author: pwizla

docs/user-docs/latest/content-manager/managing-relational-fields.md

@@ -73,3 +73,7 @@ All selected entries are listed right below the drop-down list. Click on the nam
 To remove an entry, click on the cross button ![Cross icon](../assets/icons/cross.svg) in the selected entries list.
 
 Entries from multiple-choice relational fields can be reordered, indicated by a drag button ![Drag icon](../assets/icons/drag.svg). To move an entry, click and hold it, drag it to the desired position, then release it. This is a beta feature for now. <BetaBadge />.
+
+:::tip Using the keyboard to reorder <BetaBadge />
+You can also use the keyboard to reorder relations: focus the relation using Tab, press Space on the drag & drop button Drag icon and use the arrow keys to then re-order, pressing Space again to drop the item.
+:::