Add "Unsubscribe from newsletter" page

[KastanDay]

The page is here: https://uiuc-chat-git-addunsubscribefromnewsletter-kastandays-projects.vercel.app/newsletter-unsubscribe

This is so we can include a working unsubscribe link in our emails, that's critical for deliverability.

[vercel[bot]]

The latest updates on your projects. Learn more about Vercel for Git ↗︎

Name	Status	Preview	Comments	Updated (UTC)
uiuc-chat	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	May 10, 2024 10:16pm

[KastanDay]

Current design