sloop cat’t work offline

[akr8s]

My work computer doesn't have access to the Internet, so sloop won't work properly when I access sloop web.

[akr8s]

[karlskewes]

Good call and there are additional reasons we should solve this:

1. we don't have visibility of clients requests to CDN's so we can't tell if clients requests succeed or fail. We do have http metrics for client requests directly to Sloop.
2. browsers stopped caching third party resources referenced by multiple sites due to possible privacy (tracking) implications - Chrome Blog. Sloop is single-tenant/k8s-cluster so there may be some caching across Sloop instances (same-site -> subdomain or path prefix based routing). Loss of potential caching speed up is probably offset by metrics (1) and HTTP2 (speed).

We can probably vendor in the various files instead of relying on CDN?
See: index.html

[hoerup]

Related to #208