Prepare for repo archive by creating redirect to cisa.gov/directives externally

[h-m-f-t]

With directives now hosted on cisa.gov directly, this repo is no longer maintained. The one function the Federalist/cloud.gov Pages site still performs is redirecting to cisa.gov (see #320). Since "cyber.dhs.gov" is featured in many non-CISA pages and documents, there should be a redirect from cyber.dhs.gov to cisa.gov that happens outside of this project. This should be a web-centric solution, as there are a bunch of other DNS-y things happening in the cyber.dhs.gov zone.

DNS for the cyber.dhs.gov zone is managed in Route53. One idea to maintain a redirect is to use R53 + S3, but there may be better approaches.

cc: @dav3r @felddy @jsf9k @mcdonnnj as Maintainers of the Zone 🦸 for ideas.

[jsf9k]

Given that we don't need path forwarding, but we do require HTTPS and HSTS, the best solution is to create a CloudFront distribution from a static website (just a 301 redirect) in an S3 bucket with a Lambda@Edge to inject the security headers. We have done this before, e.g. here.

[dav3r]

I haven't looked at this code in a while, but it may be a slightly more modern example than what @jsf9k linked to (or it might be almost identical). Whoever takes this on can look at both for reference.

[jsf9k]

For posterity, we would need to redirect to here.