Pre-visualization before drop

tem Pre-Visualization Before Drop

When dragging a new item into the scene:

- Show a **ghosted preview** of the item before placement
- This preview should respect snapping rules defined above (including key to toggle snapping off)
- The creator can cancel the drop before letting go of the mouse button

With this we prevent the scenario shown in the video in the intro of the shape

- Items appear fully above ground
- It’s easy to drop an item over another existing item like a table
- Creators know the true dimensions of the object they’re adding
- After the initial drag action, creators may may not need to do any further adjustments

We need to have feedback instantly. Since the model may take a couple of seconds to load, the ghost model should have two stages:
1) We display a temporary bounding box with the item’s dimensions.
Note: The bounding box dimensions is instantly available on the item’s metadata: https://github.com/decentraland/creator-hub/pull/1055
2) Once the model is loaded, we swap to the actual model.