Undo/Redo Functionality in Diagram View

[Tethik]

From user feedback. It would be useful if the standard undo/redo functionality existed. This would help against accidentally deleting components.

There might be an easy way to implement this using redux, since that's very much what the framework was originally built for.

Given that Gram is collaborative over websocket, it might be a bit tricky to accomplish.

For inspiration:
https://redux.js.org/usage/implementing-undo-history