Lazy-loading the main part of the app (#197)

* Splitting main part of app out of the main bundle.

Also improving the transition from intro to compressor.

* Showing error if app fails to load.

* lol these aren't async

* Please don't tell anyone I did this

* Spinner if user selects a file before the app has loaded. (#208)

src/components/intro/index.tsx

@@ -1,6 +1,6 @@
 import { h, Component } from 'preact';
 
-import { bind, linkRef, Fileish } from '../../lib/util';
+import { bind, linkRef, Fileish } from '../../lib/initial-util';
 import '../custom-els/LoadingSpinner';
 
 import logo from './imgs/logo.svg';