Design: `Button` with `Link` styling

[cathystoli]

In order to maintain accessibility, "links" that do not lead to a new page, ie open a modal, should be "buttons" using the html "< button >" tag. Because this is important for accessibility, we should make it easy to do through the design system.

This ticket: Create a "LinkButton" component which has all of the styling options of a link, but renders an 'button' tag and accepts button props.