docs(readme): list all five shipped templates in Available templates table

[ulises-jeremias]

Context

The cpa-templates README "Available templates" table currently lists only fastapi-starter, but templates.json ships five templates.

Steps

1. Open templates.json and read every entry under templates[] (slug, type, description).
2. Update the README table so each shipped template has a row with link, type, and one-line use case.
3. Keep table formatting consistent with the existing markdown style.
4. Do not change templates.json.

Acceptance criteria

• Table includes fastapi-starter, cli-starter, celery-worker, django-api, and uv-workspace-starter
• Each row links to ./templates/<slug>
• Descriptions match (or closely paraphrase) registry text
• Markdown renders cleanly on GitHub

Files

• README.md (edit)
• templates.json (reference only)

How to verify

Preview the README on GitHub (or locally) and confirm all five templates appear with correct links.