Add Closing-Doors triptych PSA set provided by CX

[jzimbel-mbta]

Asana task: ad hoc

(Stored directly in the project instead of S3, and bundled into the client, due to the requirement that we limit data requested from triptych screens)

I also built a test client package to confirm that the start-playback-on-onscreen mechanism works—it does. Relevant slack thread

• Tests added?

[github-actions]

Coverage of commit ace935d

Summary coverage rate:
  lines......: 40.8% (2287 of 5612 lines)
  functions..: 42.1% (1047 of 2486 functions)
  branches...: no data found

Files changed coverage rate: n/a

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