Custom blocks do not have a quick move animation

When quick moving items around the inventory or into containers, a "flying item" is displayed to visually convey this movement. However, this animation is absent for custom blocks resulting in the custom block vanishing for a noticeable amount of time when moved.

Steps to Reproduce:

1. Install and apply the provided behaviour pack which adds a custom block to the "Construction" tab in the creative menu.
2. Give yourself the custom block and move it around the inventory by holding down Shift and clicking on the item.

Observed Results:

No flying item is displayed.

Expected Results:

Custom blocks have the same flying item animation as every other item.