[DBEX] add mental health conditions screener page

[freeheeling]

Are you removing, renaming or moving a folder in this PR?

• No, I'm not changing any folders (skip to TeamSites and delete the rest of this section)
• Yes, I'm removing, renaming or moving a folder

Did you change site-wide styles, platform utilities or other infrastructure?

• No
• Yes, and I used the proxy-rewrite steps to test the injected header scenario

Summary

• (Summarize the changes that have been made to the platform)
  • Create the first (screener) page of the new, digitized Form 0781 flow (page design)
• (If bug, how to reproduce)
  • n/a
• (What is the solution, why is this the solution)
  • Create a new flow and pages to align the digital form with the VA Form 21-0781 paper version
• (Which team do you work for, does your team own the maintenance of this component?)
  • Disability Benefits Experience Team 2 (dBeX Carbs 🥖), which owns maintenance of all files in this PR
• (If using a flipper, what is the end date of the flipper being required/success criteria being targeted)
  • sync_modern_0781_flow will be utilized for specific users until all who start a new form and claim a new disability will be routed through an alternative 0781 flow

Related issue(s)

• [0781 PS] Screener Page Skeleton va.gov-team#96933
• [Epic] 0781 Paper Sync  va.gov-team#87438

Testing done

• Describe what the old behavior was prior to the change
• This page did not previously exist on the digital form
• Describe the steps required to verify your changes are working as expected
  1. enable sync_modern_0781_flow toggle
  2. start a new claim
  3. the new page, Mental health conditions, should display after the 'Prisoner of war (POW)' page in the Disabilities chapter
  4. the new page should continue to the 'Additional disability benefits' page
• Describe the tests completed and the results
  • added unit tests
  • manually tested

Screenshots

	Mobile	Desktop
collapsed
expanded
invalid

What areas of the site does it impact?

• 526 EZ

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 (linked page does not exist)

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

• Did you login to a local build and verify all authenticated routes work as expected with a test user