Add image-map appearance for selects

### Description
The `image-map` appearance on selects makes it possible to display choices as regions on an SVG.

[Collect docs](https://docs.getodk.org/form-question-types/#select-from-image-widget)

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### Checklist
- **Does it need UI/UX design?**
- [x] Yes. Describe the UI/UX requirements or attach a Figma link in the "Design" section.
- [ ] No
- **Does it need API design?**
- [ ] Yes. Specify the endpoints, methods, or data structures needed.
- [x] No
- **Does it need design around state flow?**
- [x] Yes. Outline the state flow requirements.
- [ ] No
- **Does it need a test plan?**
- [x] Yes. Add the test plan as a comment in this task or attach the document.
- [ ] No
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### User Stories

- **As a** form user,
**I want** to select choices from an image,
**so that** I can easily make the right choice when the real-life selection is visual or I am non-literate.

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### Design

- **Figma**: [Insert URL]
- **Design Docs**: [Insert URL]

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### Dependencies

-

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### Additional Notes

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### Related Issues

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The issue names no implementation files, entry points, or tests, and its Design and test-plan sections are still placeholders. Start by locating the existing select appearance handling and reviewing the linked ODK documentation. Done should include a defined design and state flow for selecting choices as regions on an SVG, plus an agreed test plan.

Written by the indexing model from the issue text.