Add 'Undo' to Todos in the Done tab

In !8691 (merged), we added the capability to 'Undo' marking a todo as complete. These feels great, makes me feel more in control, and that content doesn't shift under my cursor. A next great step would be to add the ability to 'Undo' all the todos marked complete in the 'Done' tab of the Todo dashboard.

The undo functionality added in !8691 (merged)

Proposal

Since you didn't just mark these todos as complete, the term 'undo' doesn't make sense. However, we could just take a cue from the issue itself and add a Add todo button.

Current	Proposal