Component `fallback` and `disconnect` VDOM

[Archmonger]

Current Situation

There currently is no convenient way of reacting to WS disconnection within components without doing so in the JavaScript websocket.onclose event.

Proposed Changes

Allow all components to have a

• fallback=...
  • Pre-generated HTML when the initial render (client's first WS connection) couldn't occur
  • Probably only feasible to exist on a top level component
    • ex. @component(fallback=...)
  • Probably will be reliant on template tags
    • Maybe this fallback HTML is serialized as a string?
• disconnect=...
  • Pre-generated HTML displayed in the event of a websocket disconnect

Implementation Details

See here for more details.

[Archmonger]

I've expanded the concept of this one to fallback and disconnect as separate entities for flexibility.

[Archmonger]

Closing this in favor of #653