Lock an item to a specific position

[mhuggins]

Is your feature request related to a problem? Please describe.
I'm interested in having a specific item always appear in a locked position within the masonry layout (e.g.: top-right column/cell).

Describe the solution you'd like
The item should be able to appear in a location position, no matter if I add or remove items & re-render the Masonry component.

Describe alternatives you've considered
I have not considered alternatives, though I'm going to see if this can be done with the usePositioner hook in its current form.

Additional context
N/A