Undo/redo actions support

[mapmeld]

Description

• Adds undo and redo buttons with radix-icons for Undo and redo #69

• There is an undo stack (recentZoneAssignments, to reverse the last mousedown -> mouseup draw action.
• Once you undo an action, the "Redo" button is enabled and it reapplies draw actions
• Because undo/redo use setFeatureState and setZoneAssignments, they update the map, chart, and serverside doc
• If you undo and then draw new districts, the future Redo-able actions are erased
• A new flag prevents Undo/Redo from adding its actions to the undo stack

Remaining issues

• Better integration into drawing UI
• Object.keys(..).forEach(...) was odd syntax to re-apply zone draws, could be refactored & consider issues with debouncing if we update several zones at once
• Limit the number of actions in the undo stack (did 7) before erasing the first actions
• Doesn't work with changes to zones from the original map load, because those are not in state.zoneAssignments

[mapmeld]

I set a limit of 7 undo-able actions, and removed a call to resetZoneAssignments() which cleared the assignments which had been loaded from a saved map.

[nofurtherinformation]

Hey @mapmeld! What would you think about using this undo/redo middleware for zustand? I think this will be ultimately less code to maintain, and with the changes coming down in from Shattering the map rendering happens as subscriptions/side-effects of state changes which should make the app and map state easier to observe