Add support for List item tags and link types

[mattsherman]

Infrastructure work in preparation for #4082 (Quick Links)

• General
  • Adds support for showing console.log messages in Storybook, making it easy to verify interactions (added @storybook/addon-console as a dev dependency)
• Link component
  • Adds Storybook stories for all Link types (wp-admin, wc-admin, external)
  • Adds unit tests for Link component
• List component
  • Adds setting of List item link type
  • Adds onListItemClick prop
  • Adds listItemTag item prop
  • Adds item click and tag example to Storybook
  • Adds unit tests for List component

See draft PR #4292 for a look at how these changes to List will be used by the QuickLinks component in the new home screen. In particular, the item tagging and click support will be used to hook in Tracks events (not implemented yet in #4292).

Screenshots

Detailed test instructions:

Storybook

npm run storybook

Unit testing

npm test -- -i packages/components/src/link/test/index.js packages/components/src/list/test/index.js

Optional: Confidence check

• Make sure that List changes haven’t affected other use of List in wc-admin, such as task list

Changelog Note:

• Infrastructure work - no changelog note needed

[psealock]

Nice thorough work here @mattsherman !

Just a couple thoughts on links, although I may be not understanding correctly here. Its also nice to see some test coverage too. I found this article really helpful and noted a few things that I learned: https://kentcdodds.com/blog/common-mistakes-with-react-testing-library

I'm pretty impressed with how well getByRole works and how it mimics how a user or screen reader would scan a page. Just a few suggestions, but pre-approving.

[mattsherman]

Thanks for the review @psealock! I addressed all of your feedback prior to merging.