v0.3 - Vertex Snapping & Undo/Redo

This small release includes 3 helpful tools for a good UX when laying out assets in the scene:

# Vertex Snapping

1. select the tool in the top toolbar
2. press the left mouse button on the vertex that will be snapped
3. release the mouse on the vertex to snap the first one to

Here's the tool in action:

# Undo / Redo

Less impressive but quite useful too, undo/redo has be added, covering all actions. `Ctrl+Z` to undo, and `Ctrl+Shift+Z` to redo! An action log has also been added (right panel by default), to get an idea of where we're at in the history.

# Duplicate Selection

Finally, it's now possible to duplicate the selection with `Ctrl+D`.