Add checkboxes to checklist items

Currently the site has no mechanism to let a user check off something in the checklist to mark it as reviewed.

We should add the ability for someone to check each item on the Checklist page off to indicate completion.

• Incorporate a checkbox pattern
• Make sure it does not have nested interactive control issues, especially with screen readers/voice control
• Use localstorage to persist checked/unchecked state between sessions