Deselect on click

[Alecaddd]

Summary / How this PR fixes the problem?

Initial tiny PR to start implementing a more standard selection/deselection paradigm for multiselect. This PR implements the ability to deselect all items if a click happens in an empty area between selected items.

Steps to Test

• Create multiple items
• Add items to selection by holding SHIFT
• Click on an item and drag to move the entire selection (no deselection should happen)
• Click on an empty area between selection items and drag to move the entire selection (no deselection should happen)
• Click on an empty area between selection items (the selection should be reset)

Known Issues / Things To Do

• Clicking on an item that is part of a selection without dragging should deselect all items except the clicked on. Will do in a follow up PR.
• I feel like the code could be better optimized, but I need to get acquainted with the new architecture before I can make these calls.

[Alecaddd]

Auto approving and merging this since it's a minor change and has been 3 days. We can always fix and improve things later.