Beehiiv RSS feed is a feature of the Beehiiv. Beehiiv is a relatively young, hosted newsletter platform built for businesses and creators.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.
Vercel is a cloud platform for static frontends and serverless functions.