Dart-flute-wasm doesn't run unless index.html is in the URL

[mstange]

This is a regression from #52.

Running https://webkit-jetstream-preview.netlify.app/ stops during Dart-flute-wasm with "Uncaught (in proimse) TypeError: can't access property 1, location.pathname.match(...) is null"

Using https://webkit-jetstream-preview.netlify.app/index.html works.

[mstange]

Can you take a look, @kmiller68?