[WIP] Link component with cloneElement

[haworku]

Summary

• Adds new Link component
• Uses PossibleLinkProps union type.
• variant prop adjusts styles. Style as button by using variant: 'unstyled' and passing in custom classes

Random learnings about types

• Typescript doesn't seem to have a straightforward XOR type. Union types are not exclusive
• Overloads seem to mostly address the issue (errors when expected, though messages can be strange).

Note on broken "visited" storybook example

The "visited" link story example isn't working. I think think is related to #191. Styles aren't being inherited from custom stylesheets.

Related Issues or PRs

• closes [feat] Link Component #145
• Button should take a Component prop #161

How To Test

• See new Link component stories

[haworku]

I've pushed a new commit of how this could work using cloneElement instead of createElement. This could be a more straightforward way to simply add the styles (props) we want for link. It also keeps prop types contained. Welcome any feedback on this - I'm new to both of these patterns.

[haworku]

Closing in favor of #309