web: run a public deployment of the latest release in --read-only mode

[sudoforge]

instead of including many independent screenshots of the web UI, we should host it so that users can browse git-bug issues with the latest release of the web ui to experience what it's like.

this deployment would be unauthenticated, and only expose the web ui in read-only mode.

it should:

• leverage anubis for request filtering
• be in a private network, exposed via a load balancer
• auto scale based on load to some reasonable amount (we won't scale infinitely, but we should configure a modest upper limit to handle surge traffic, e.g. from HN or TLDR posts)
• be immutable - build the image in a pipeline, block all non-http(s) traffic
• periodically run git bug pull to stay up-to-date
• be updated as part of the release pipeline (perhaps a second deployment for HEAD in the future)

it does not need any authentication to pull from the https remote.