feat: auto-layout

[dalechyn]

Is your feature request related to a problem? Please describe.
When you create a new node, it usually is created at the right of the last child node, which breaks the visual appearance of a tree.

Describe the solution you'd like
Add automatic layout positioning feature.

Additional context

• https://reactflow.dev/docs/examples/layout/auto-layout/

[transmissions11]

agreed auto layout would be a useful option (like auto zoom), but don't want to force it on everyone as some folks like dave like to layout their trees in funky ways.

[dalechyn]

@transmissions11, absolutely! It makes sense to enable this on some key-hit, as it would be not effective to force it on every node addition.