feat: support setting drop effect for drop targets.

[josephdangerstewart]

Adds an option to the useDrop hook to set the drop effect based on drop target and updates the documentation to reflect the changes.

Since there can be multiple sources of truth for what the drop effect should be (drag source options, drop target options, and alt key being pressed), my PR uses the following precedence (but I'm happy to change it if the reviewer prefers something different)

1. Use dropEffect from drag source
2. Use dropEffect from the most deeply nested drop target
3. If the alt key is pressed, then use "copy"
4. Default to "move"

Resolves: #3529