Back to top component for Police MVP

[xiongjaneg]

Description or Additional Context

Back to top component guidance according to the Usage: In pages with static content that is more than two screens in length on large and medium screens, or more than four screens in length on small screens.

For the MMVP, the police page is two screens and doesn't fall under this guidance, so the component wasn't added.

For MVP, after police activity is added, the page length and applicability of this guidance will need to be reviewed and updated, if needed.

Acceptance Criteria

• [x] MVP has back to top component.
• [x] Requires design review
• [x] Requires accessibility review

[mmiddaugh]

Related: #13879 Evaluate "Back to top" component for VAMC pages

[mmiddaugh]

Note: this component is not yet flagged as USWDS V3 ready

[jilladams]

design / a11y signed off in PR just needs prod deploy and verification Monday.

[jilladams]

Deployed to prod, ~but no prod content available to verify~ - this is Police, not VBA. Verified in prod: