[website][docs] Website all assets missing and redirect not working

The github hosted website's assets (styles, images, js) are completely gone and github website doesn't redirect.

https://facebook.github.io/relay/

Only https://relay.dev/ works now

Might have been introduced by https://github.com/facebook/relay/pull/2754 which was suppose to redirect.

@kassens

Start by opening the linked pull request #2754 and inspecting the GitHub Pages or redirect configuration associated with https://facebook.github.io/relay/. Verify how the site is deployed and how assets are referenced; the work is done when the hosted URL redirects correctly and styles, images, and JavaScript assets load as expected.

Written by the indexing model from the issue text.