WIP: add storybook

Try it

1. git checkout 34046-storybook and yarn to install deps
2. Storybook loads styles served from GDK, so GDK needs to be running on port 3000. For other ports, configure in .storybook/preview-head.html. This will change with scss-loader, or when I think of something better
3. run yarn storybook to start storybook dev server
4. visit localhost:6006
5. To edit stories, go to stories/index.js

See docs/examples/etc in https://storybook.js.org/

SPIKE to add storybook to test Vue components

Example rendering Widget with the contents of spec/javascripts/vue_mr_widget/mock_data.js Can add different values to the bottom to switch between states, or save combinations on the left side

TODO:

• add styles. can either add CSS file to template, or wait for sass loader
• remove camelize
• remove default stories
• add some examples

What does this MR do?

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #34046 (closed)