feat: Conditional Logic: back button

[thiessenp-cds]

Summary | Résumé

This PR builds on the group history navigation by adding the ability to go to a previous form answer using a back button.

To see a demo, here is Stevie Ray's PR environment

[timarney]

Tested and will approve

Noting it's slightly odd that the styling of the buttons change as you reach the end.

cc: @samsadasivan