Draft: PoC Render to string

[MadLittleMods]

Just some proof of concept work to see if renderToString would be possible to facilitate server-side rendering.

Please ignore.

Related to #653

It sorta works:

What it looks like from #653 (expected)	This PR (actual)

Dev notes

const view = new TimelineView(timelineViewModel);
// view.mount() now returns a string of HTML
app.insertAdjacentHTML('beforeend', view.mount());

Problems

• Some render() functions have DOM side-effects
• t.view(...) causes a lot of side-effects since it calls mount() (which has side-effects), then render()
  • In my use, the ListView which is an IView and does a bunch of mount document.appendChild stuff
  • A TemplateView is much more compatible since we can just render and get a string mostly