feat: adding Storybook to Superset (#10383)

* Storybook added!

* starting to configure junk....

* Storybook works!!!

* Now with theme!

* apache boilerplate

* more apache comments

* lots o' knobs for the Button.... taking stock of the codebase

* more classes, but killing the knob for now.

* nixing unused module

* linting

* fresh package-lock

* now with tooltip!

* adding path and zlip because the linter told me to

* upgrading storybook packages from devdeps

* linting

* removing cruft

* killing an annoying (and old?) lint issue

* lint fix, take 2.

* removing zlib/path

* package lock reset from master

* re-adding new packages for this here PR

* nixing console log, simplifying

* nixing comment TODOs (done enough!)

* basic docs.

CONTRIBUTING.md

@@ -703,6 +703,17 @@ npm run cypress open
 
 See [`superset-frontend/cypress_build.sh`](https://github.com/apache/incubator-superset/blob/master/superset-frontend/cypress_build.sh).
 
+### Storybook
+
+Superset includes a [Storybook](https://storybook.js.org/) to preview the layout/styling of various Superset components, and variations thereof. To open and view the Storybook:  
+
+```bash
+cd superset-frontend
+npm run storybool
+```
+
+When contributing new React components to Superset, please try to add a Story alongside the component's `jsx/tsx` file.
+
 ## Translating
 
 We use [Babel](http://babel.pocoo.org/en/latest/) to translate Superset.