Develop usa-link Web Component

[heymatthenry]

One of the first components we'll recreate as a Web Component is the usa-link (uswds/uswds#5706).

Necessary Tasks

These are the features that should constitute MVP for the pre-release version, since they will help us get our arms around the architectural choices we'll have to make in developing further components.

• Add more vitest unit tests for component
• Evaluate component's accessibility shortcomings and document them
• Add a Storybook story for the component (Depends on Configure Storybook #6)

Stretch Goals

All of these will need to happen at some point, but don't necessarily have to happen for the pre-release version

• The current WIP implementation (Add usa-link component #8) for this component renders a link to the shadow DOM. Consider revising that implementation so that the the full link goes in the component <slot>.
• Figure out how to package the component by itself for distribution (Depends on Configure monorepo to build component packages #5)
• Remediate any accessibility bugs