Banner on home page for announcements

[edwardshturman]

Useful for hoisting important upcoming events e.g. DEPLOY/25

Similar to the banner we'd show on the BLOOM platform

Maybe: connected to Edge Config

[edwardshturman]

Next steps:

1. (Async) get set up by cloning compsigh/web, installing the vercel CLI (npm i -g vercel), pulling environment variables (vercel env pull)
2. (Sync) design work together on the banner: Tuesday 2:30