Undo/redo

[Phanabani]

This is a very large task, but it could start more simply as only supporting undoing/redoing object transformations.

[MilchRatchet]

I would also advise to only focus on undoing/redoing object transformations. Adding/Deleting objects does not work properly yet anyway so we should do the undo/redo for that at some later point. (I am not sure whether adding objects even exists right now but deleting objects often causes the game to crash so it working in the editor is a deception)

[Phanabani]

We can use #62 to chunk interactions that will push to undo state (e.g. click, drag, release to transform = 1 interaction, not hundreds of small movements)