Modal tests

[ofhope]

Fixes #issue-number

This PR adds storybook documentation and unit tests to the modal component.

It also looks like a bable upgrade along the way broke storybook hot module reloading.
I didn't spend a lot of time investigating the cause but did find a solution to monkey patching the issue. HMR was still working in storybook but un-viewable without this patch.

Changes:

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123

[lindapaiste]

It also looks like a bable upgrade along the way broke storybook hot module reloading. I didn't spend a lot of time investigating the cause but did find a solution to monkey patching the issue. HMR was still working in storybook but un-viewable without this patch.

THANK YOU! I've been seeing that error but hadn't had a chance to look into it yet.

[lindapaiste]

Looks great! I love the tests for the inside and outside click behavior and I so grateful for the window.$RefreshReg$ fix.

[lindapaiste]

It's a bummer that it doesn't render with the proper styling. There's two issues there, one of which I only just now realized! Maybe you can fix it in a separate PR.

1. The modal needs to have a parent with class="light" (or "dark" or "contrast"). This will be fixed by Add theme switching to Storybook #2326, but we can also put in a quick fix until that gets merged since it might be a while. We can add a <div className="light"> to the decorators in preview.js.
2. The compiled main.css file that we are importing in preview.js is not up to date. I don't know what that file is for and probably it should be deleted. We want to import the uncompiled file import '../client/styles/main.scss' as that will be current will all changes. But in order to do that we also need a Storybook addon to process it: https://storybook.js.org/addons/storybook-addon-sass-postcss