Add item counter to the add another component

[simonwhatley]

Summary

When adding 2+ items using the add another component, show a count next to each item heading to help orientation.

Additional context

• When only one item is on the page, do not show a count. (Similar interaction to the remove button)
• When clicking add another button, add the appropriate number next to each item. E.g., Item 1, Item 2
• When removing items, recalculate the item numbers. E.g., removing Item 2 from a list of 3 things will re-number Item 3 as Item 2.