report(flow): standalone shell report with preact

[adamraine]

Basic shell for a FR flow report. It doesn't actually render the report, I'm hoping to use the updated renderer API for that part #12772.

In the meantime we can work on the flow UX items like the sidebar and summary page.

Example report: https://gist.github.com/adamraine/7bf5b5b3c8a3f08cbf1226cddaeff078

Ref #11313

[connorjclark]

Can you add the result to lighthouse-core/scripts/build-report-for-autodeployment.js so we can easily preview it? Not much to see now I know, but might as well set it up for the near future.

[patrickhulce]

I had quite a hand in most of this, so I'm most interested in other folks feedback :)

but tsx sounds great to me!