Set up Storybook

[shawnbot]

This brings Storybook into the repo as a more feature-full environment for testing our form features and individual components. You can see it in action at on Heroku.

The setup was honestly kind of painful. Some notable pain points:

1. I first tried the Storybook web components framework to see if we could use the <sfgov-form> component as the foundation for testing. Unfortunately, a lot of things were missing and I couldn't even get the controls or actions addons working.
2. I wanted to use the official formio/react package, but I couldn't figure out (in Storybook's wacky webpack setup) how to bundle it and our theme in such a way that they share the same Formio reference. Instead, I built a new Form (React) component that uses state and effect hooks extensively, and it seems to work well; but it feels like a hack.

@JimBrodbeck Could you review this while I'm out? I'd love your thoughts on a couple of things:

1. Are you able to npm install and then run Storybook with npm run storybook?
2. Does the way that stories are written make sense?

[github-actions[bot]]

Size Change: -3.35 kB (-4%)

Total Size: 86.5 kB

Filename	Size	Change
dist/formio-sfds.standalone.js	66 kB	-3.4 kB (-5%)	✅
dist/portal.js	6.7 kB	+53 B (+1%)

ℹ️ View Unchanged

| Filename | Size | | :--- | :---: | | `dist/formio-sfds.css` | 13.8 kB |

_{compressed-size-action}

[shawnbot]

We will not be doing this 😄