Add newsletter template

[pfstr]

Newsletter template

A self-hosted, serverless newsletter that runs entirely on the user's own Cloudflare account: a hosted (and embeddable) signup form, one-click RFC 8058 unsubscribe, and a simple /admin page to send a campaign. Subscribers live in D1, so the user owns the data.

Sending is deliberately provider-agnostic: src/email.ts is a small sendEmail() adapter the user wires to their own email provider, so the template ships tied to no vendor. Collecting subscribers works out of the box with zero configuration.

Optional, off by default

• Double opt-in (DOUBLE_OPT_IN) — a confirmation-email step before a subscriber is added
• Bot protection via Cloudflare Turnstile on the signup form
• Automatic RSS → email on a cron trigger, with a first-run baseline and per-post dedup so posts are never emailed twice

Products & bindings

• Workers + D1
• Handlers: fetch (Hono) and scheduled (cron trigger)
• Deploy-screen config: ADMIN_TOKEN, FROM_NAME, FROM_EMAIL, DOUBLE_OPT_IN

Notes for reviewers

• E2E tests in playwright-tests/newsletter-template.spec.ts using the shared fixtures.
• preview_image_url / preview_icon_url left out for the Growth team to provide; a screenshot is included in the README for now.
• Contributor-hosted live demo while in review: https://newsletter-template-preview.rafael-pfister.workers.dev