Adds registry entry for new form app (21-4140).

[ryguyk]

DO NOT MERGE
Must merge vets-website PR first.

Summary

Adds an entry to registry.json for a new app added in vets-website (simple-forms-form-engine/21-4140).

Related issue(s)

Original ticket: department-of-veterans-affairs/va.gov-team#96075
vets-website PR with added app: department-of-veterans-affairs/vets-website#32891

Testing done

N/A. Simply a registry addition.

Screenshots

N/A

What areas of the site does it impact?

Simply a registry addition.

Acceptance criteria

Quality Assurance & Testing

• I fixed|updated|added unit tests and integration tests for each feature (if applicable).
• No sensitive information (i.e. PII/credentials/internal URLs/etc.) is captured in logging, hardcoded, or specs
• Linting warnings have been addressed
• Documentation has been updated (link to documentation *if necessary)
• Screenshot of the developed feature is added
• Accessibility testing has been performed

Error Handling

• Browser console contains no warnings or errors.
• Events are being sent to the appropriate logging solution
• Feature/bug has a monitor built into Datadog or Grafana (if applicable)

Authentication

N/A

[derekhouck]

LGTM. Approving now so it can be merged once the other PR is good to go.